CBM and chargeable weight in freight

Chargeable weight is the figure a freight rate is multiplied against: the greater of a consignment’s actual gross weight and its volumetric weight, where volumetric weight is the cargo’s volume converted to a weight through a divisor the carrier sets for that mode. CBM, the cubic meter of cargo, is the volume input to that comparison. Dense cargo bills on the scale; light cargo bills on the space it occupies.

The divisors are not the same across modes and they are not regulated. Air uses 6,000 cubic centimeters per kilogram under IATA TACT Rules 3.9.4, express integrators use 5,000, sea groupage uses the weight or measurement basis at 1,000 kg per cubic meter, and European road groupage abandons the cubic divisor altogether for the loading meter. Pick the wrong one and an invoice comes back at a different order of magnitude from the quote. This article covers the arithmetic, the four divisors with their sources and their rounding rules, the full-container-load crossover, the volume and payload ceilings of an ISO container, the verified gross mass rule that has governed how a packed box is weighed since 1 July 2016, and the road weight law that usually binds before any of them.

CBM: the cubic meter of cargo

CBM is the volume a consignment occupies, in cubic meters, computed as length times width times height per package and summed across the consignment. Carriers sell capacity, and on a trailer, in an aircraft hold or inside a container that capacity fills by volume long before most mixed cargo reaches a weight limit, so the volume figure is what tells a carrier how much of its aircraft or its box a shipment has consumed.

Computing CBM from package dimensions

Measure each package in meters, multiply the three dimensions, then multiply by the number of identical packages. A carton 120 cm by 80 cm by 100 cm converts to 1.2 by 0.8 by 1.0, which is 0.96 CBM, so one hundred of them are 96 CBM. Where the consignment mixes carton sizes, compute each size group and add the groups; there is no average that survives contact with a rate sheet.

The units error is the one that moves a quote by orders of magnitude. One cubic meter is 1,000,000 cubic centimeters, not 10,000 and not 100, because the 100 cm per meter conversion cubes. Convert every dimension to meters before multiplying rather than converting the product afterward, and sanity-check the result against a physical object: a one-meter cube is 1.0 CBM, a shoebox is a few thousandths.

What the carrier measures, and how it rounds

Freight is measured on the outer package, not the goods, and the figures a carrier quotes from are the ones declared on the commercial invoice and packing list . The dimensions that count are the ones a forklift and a stow plan see: the carton wall, the pallet footprint, the pallet base height, and any overhang past the pallet edge. A 1.2 m by 0.8 m Euro pallet loaded to 1.6 m is billed at 1.536 CBM whether the cartons on it total 1.5 CBM or 1.1.

Air cargo goes further and measures to the bounding box. IATA TACT Rules 3.9.4 takes the greatest length, the greatest width and the greatest height of each piece, so a drum 0.6 m in diameter and 0.9 m tall measures 0.6 by 0.6 by 0.9, which is 0.324 CBM against the 0.254 cubic meters its cylinder actually displaces. That 28 percent difference is not an error in the tariff. It is the tariff charging for the cuboid of hold space the drum sterilizes.

Rounding is the detail most quotes get wrong. TACT 3.9.4 rounds each dimension in both directions, 0.5 cm and above up and 0.1 to 0.4 cm down, so 67.7 cm becomes 68 cm while 11.3 cm becomes 11 cm. The volume weight is then computed to three decimal places, and only the final chargeable figure is rounded to the next half kilogram, with 0.51 to 0.99 kg taken up to the next whole kilogram. Express integrators round differently: FedEx rounds each dimension up before multiplying, which produces a slightly larger figure on the same carton.

Why carriers price volume at all

Density across the cargo book spans three orders of magnitude, and a weight-only tariff loses money on every low-density load. Bagged cement runs above a tonne per cubic meter; expanded polystyrene packaging runs a few kilograms. A shipper of foam billed only on the scale would fill a trailer for almost nothing while displacing paying freight, which is the commercial problem the divisor exists to solve.

Pricing on the greater of weight and volume closes that gap in one operation, and the point at which the two measures change places is the mode’s break-even density. That density, not the divisor itself, is the number worth memorizing, because it tells a quoter which side of the comparison a given cargo will land on before any arithmetic is done.

Chargeable weight: the greater of two numbers

Chargeable weight is the greater of the actual gross weight and the volumetric weight, computed for each consignment against the divisor in the governing tariff. If the actual weight wins, the carrier is selling tonnage and the cargo is dense. If the volumetric weight wins, the carrier is selling space and the cargo is light. The rule is identical across air, express, sea groupage and road; only the divisor changes.

The divisor is a contract term, not a constant

No public authority sets a dimensional-weight divisor. The air figure lives in the IATA TACT Rules, which are an inter-carrier trade-association publication rather than a regulation, and the express and road figures are carrier tariffs revised on an annual cycle. The distinction is not academic: the antitrust immunity that once covered collective IATA tariff setting has been withdrawn on both sides of the Atlantic, with the European Union phasing out the block exemption for tariff consultations under Regulation (EC) No 1459/2006 across 2006 and 2007, and the US Department of Transportation withdrawing approval of the IATA traffic conference agreement for cargo rates with effect from 30 June 2007. Coordinated surcharge setting is now a cartel offense, which the European Commission confirmed when it re-adopted fines of EUR 776,465,000 against 11 air carriers on 17 March 2017 for fixing fuel and security surcharges.

So the only authoritative divisor for a shipment is the one in that carrier’s published tariff or in the negotiated rate sheet, alongside the ocean freight rates it is quoted with, and a forwarder or NVOCC is free to buy on one divisor and sell on another. That spread is ordinary consolidator margin, and it is why comparing quotes means comparing chargeable weights rather than rates per kilogram.

Break-even density by mode

The break-even density is the reciprocal of the divisor, and it is the density at which volumetric weight and actual weight coincide. Air at 6,000 cubic centimeters per kilogram breaks even at 166.67 kg per cubic meter. Metric express at 5,000 breaks even at 200 kg per cubic meter. Sea groupage on the weight or measurement basis breaks even at 1,000 kg per cubic meter, six times denser than air.

A single consignment can therefore sit on opposite sides of the line in two modes at once. Cargo at 400 kg per cubic meter is dense by air, where it bills on its scale weight, and light by sea, where it bills on its cube. That is not an inconsistency in the tariffs. It reflects what is actually scarce: volume in an aircraft hold, and both volume and deadweight in a ship.

The divisors by mode

Four conventions cover almost all general cargo: the IATA air standard, the express integrator tariffs, the sea weight or measurement basis, and the European road loading meter. Each carries its own divisor, its own rounding, and its own view of what a billable unit is.

Air freight: IATA TACT Rules 3.9.4

Air cargo converts volume to weight at 6,000 cubic centimeters per kilogram, stated in IATA TACT Rules 3.9.4 together with its imperial siblings of 366 cubic inches per kilogram and 166 cubic inches per pound. The rule charges a consignment on volume where it averages more than that ratio, which is the same statement as the 166.67 kg per cubic meter break-even read from the other end.

The widely repeated shorthand that one CBM equals 167 kg is a rounded result, not a rate step, and multiplying by it is wrong at every volume above one cubic meter. The divisor applies to the consignment, then the answer is rounded: 2 CBM is 2,000,000 divided by 6,000, which is 333.33 kg and bills at 333.5 kg, where 2 times 167 would give 334 kg. At 10 CBM the two methods diverge by 3 kg. Small on one shipment, systematic across a rate file.

The 7,000 factor that preceded the current ratio survives inside TACT 3.9.4 itself as named exceptions rather than as history, applying to cut flowers and live plants out of India and to specific commodity rate items out of Sri Lanka. Where a shipment falls in one of those carve-outs the volumetric weight is about 14 percent lower than the general rule produces.

Two further TACT mechanics change the invoice without changing the chargeable weight. The minimum charge under TACT Rules 3.4.1 applies per consignment and overrides a low computed figure entirely. And the general cargo rate ladder steps down at 45, 100, 250, 500 and 1,000 kg, which creates the break-back point: where the next weight step’s lower rate applied to its own minimum beats the actual weight at the current rate, the shipment is declared up to that step. The crossover is the higher weight times the lower rate, divided by the higher rate.

Express and courier: 5,000 and 139

Express integrators use a harsher divisor than air cargo, and they apply it per piece. FedEx publishes 5,000 cubic centimeters per kilogram metric, with 305 cubic inches per kilogram and 139 cubic inches per pound in imperial, and rounds each dimension up. UPS publishes 139 on its daily rates and its export services, with 166 surviving on parts of its domestic retail and mail book, and its 2026 retail rate guide updated on 7 July 2026 still carries both figures on different services.

At 5,000 a cubic meter bills as 200 kg against 166.67 kg on the IATA basis, so identical light cargo carries a 20 percent higher chargeable weight before any rate difference. The per-piece application compounds it: air cargo averages the volumetric calculation across the consignment, so a dense piece can absorb a light one, while a per-piece express tariff charges every light carton on its own cube with no offset.

The imperial divisor moved from 166 to 139 in January 2017, FedEx on 2 January and UPS on 8 January. The 2015 change frequently cited in its place was a different one, extending dimensional pricing to all ground packages at the then-current 166 factor. Every one of these figures is a dated tariff term, so it carries its year or it is not a figure.

Sea LCL: weight or measurement and the revenue ton

Sea groupage bills on weight or measurement, written W/M, in revenue-ton, where the carrier takes whichever of the cargo’s weight in tons and its volume in cubic meters yields the greater revenue. A consignment of 4 CBM weighing 900 kg bills as 4 revenue tons; the same 4 CBM weighing 5,200 kg bills as 5.2 revenue tons.

The unit needs reading carefully. The US Maritime Administration glossary defines the revenue ton as whichever basis yields more revenue and warns that the weight ton may be a short, long or metric ton and that the measurement ton is usually 40 cubic feet, or one cubic meter in a metric tariff. Forty cubic feet is 1.1327 cubic meters, so a tariff billing in 40-cubic-foot measurement tons yields about 11.7 percent fewer chargeable units on the same cargo than a metric tariff does. The UK freight ton of 42 cubic feet differs again. On an old-form or break-bulk quote, establish which ton is meant before comparing anything.

Road groupage: the loading meter

European road groupage prices on trailer length, not on a cubic divisor. One loading meter is one meter of trailer length across the full loading width, computed as length times width divided by 2.4 with one dimension rounded up to a standard 0.80, 1.20, 1.60 or 2.40 m step. A standard curtainsider is 13.6 loading meters, so the basis is a straightforward share of a finite trailer.

Conversion to a billing weight is a tariff table rather than a formula, and it varies by country. One continental groupage tariff current at 8 July 2026 converts 1 loading meter to 1,850 kg and 1 CBM to 333 kg, with a Euro pallet at 740 kg, while quoting 2,000 kg per loading meter for the United Kingdom, Ireland and the Nordics, and 1,500 kg per loading meter with 250 kg per CBM for Danish domestic traffic.

The switch to the loading meter basis is conditional rather than volumetric. The published triggers include non-stackable freight, lopsided or overhanging goods, height above 130 cm, length above 240 cm, individual pieces above 30 kg, and any load requiring full-width securing. A stackable, palletized, regular load bills on the cubic conversion; the same weight of awkward freight bills on the meters of floor it sterilizes.

Rail and intermodal

No distinct chargeable-weight convention exists for rail. Rail freight is priced per wagon, per unit or per tonne, and an intermodal container move is priced per box, so the volume-to-weight conversion never arises. The question returns at the road leg of the door-to-door move, where axle-weight law rather than a divisor sets the ceiling.

The four divisors compared

This comparison is a Shipping-Wiki.com construction, assembled from the four governing tariff sources named in the right-hand column rather than reproduced from any single one of them. The status column is the point of the table: only one of these figures sits in a published international rule set, and none of them sits in law.

Worked contrast: dense against light at the same cube

Take two consignments of exactly 10 CBM, one weighing 1,200 kg and the other 5,000 kg, and run both through the air and sea bases.

By air, the volumetric weight of 10 CBM is 10,000,000 divided by 6,000, which is 1,666.67 kg, rounded to 1,667.0 kg. The light consignment at 1,200 kg actual bills on volume, at 1,667.0 kg chargeable, 39 percent above its scale weight. The heavy consignment at 5,000 kg bills on its actual weight, because 5,000 exceeds 1,666.67. One divisor, one comparison, opposite outcomes.

By sea on the W/M basis, the comparison is 10 cubic meters against tonnes. The light consignment is 10 CBM against 1.2 tonnes, so it bills as 10 revenue tons. The heavy consignment is 10 CBM against 5.0 tonnes, so it also bills as 10 revenue tons. Both are volume cargo at sea because both sit below 1,000 kg per cubic meter, and the 4.17 to 1 density difference between them changes nothing about what they pay.

FCL against LCL: where the crossover sits

Less-than-container-load bills per revenue ton of the space used, while full-container-load bills a flat rate for the box however full it is, so the cheaper option flips at the volume where the accumulating per-revenue-ton charge passes the box rate. That crossover is arithmetic on two current rates, not a constant, and the FCL and LCL distinction is worth nothing to a quoting desk until those two rates are in front of it.

Computing the crossover from two rates

The break-even volume is the all-in container rate plus the FCL fixed charges, less the LCL fixed charges, divided by the LCL rate per revenue ton. Everything in that expression moves: the box rate moves with the market, the per-revenue-ton rate moves with the consolidator’s fill, and the fixed charges differ by lane and by whether the shipper or the consignee is paying which end.

The widely repeated rule of thumb that the crossover sits at 13 to 15 CBM traces to no tariff, no index and no survey. Run the algebra across a plausible band of current rates and the answer moves between roughly 8 and 28 cubic meters on the same lane, which is a range wide enough that quoting the rule of thumb will lose money in both directions. The market level of the FCL side is observable, at least: the World Container Index , the Freightos Baltic Index , the Shanghai Containerized Freight Index and the China Containerized Freight Index all publish spot box rates on the main lanes. No comparable public index exists for LCL per-revenue-ton rates, which is a large part of why the folk figure persists.

The charges that move the crossover

LCL carries fixed costs that do not scale with the cube and therefore dominate a small shipment. Handling at the origin and destination container freight station , the documentation and bill of lading fees, and any per-shipment minimum are incurred once per consignment. On one worked LCL invoice those fixed elements were 51 percent of the total at 2 revenue tons and 10.9 percent at 13.92 revenue tons. The per-revenue-ton surcharges work the other way, multiplying with the chargeable figure: the terminal handling charges , the bunker adjustment factor , the currency adjustment factor , any peak season surcharge or general rate increase and, on the Red Sea routings, the Suez Canal surcharges that liner circulars add. The full build of the invoice these feed is covered in ocean freight cost and surcharges .

Three costs that never appear on the rate sheet also push the crossover down toward FCL. A consolidator buying space under a slot charter waits for the box to fill, so LCL transit is longer and less predictable, which raises the inventory carrying cost of the goods in motion. The cargo is handled at least four more times, at stuffing and stripping in both freight stations, which raises the damage and pilferage exposure that the Institute Cargo Clauses then price. And where a claim does arise, it is measured against the package and unit limitation under the carriage regime in the bill of lading , the sea waybill or the multimodal transport document , which for a consolidated shipment is decided by how the packages were described on the house document rather than by the value of the goods.

Timing runs the other way once the box goes FCL. A full container starts a free-time clock at destination, and demurrage and detention accrue on a shipper who cannot strip and return it. Booking a box also creates an obligation to fill or pay for it, which is deadfreight on a volume commitment in a service contract even where a single spot booking carries no such exposure.

Dense cargo and the weight side of W/M

The W/M basis penalizes weight as well as volume, so dense cargo reaches the crossover on fewer cubic meters than the volume alone suggests. A 10-tonne consignment occupying 8 CBM bills as 10 revenue tons, not 8, because the weight side wins at 1,250 kg per cubic meter. That is a 25 percent higher chargeable figure than its cube, and it pulls a consignment into FCL territory at a volume where a light cargo would still be comfortably in groupage.

Container capacity: the volume ceiling and the weight ceiling

A packed container is limited by whichever of two ceilings it reaches first: the internal volume, which is not standardized by anyone, and the payload, which is the unit’s rating less its tare. Both are routinely quoted from generic tables that do not apply to the box on the quay.

What ISO 668 standardizes, and what it does not

ISO 668:2020 , the seventh edition dated January 2020, classifies series 1 freight containers by external dimensions and states their ratings. It does not publish cubic capacity. Clause 1 says so explicitly, routing internal dimensions to ISO 1496: “The dimensions of each type of container are defined in the appropriate part of ISO 1496, which is the authoritative document for internal container dimensions.”

What ISO 668 does fix is the outside of the box and the floor under the inside. External length is 12,192 mm for the 40 ft classes with a tolerance of 0 to minus 10 mm, 6,058 mm for the 20 ft classes at 0 to minus 6 mm, and 13,716 mm for the 45 ft classes. Width is a uniform 2,438 mm across every series 1 container. Height is 2,896 mm for the 9 ft 6 in designations 1EEE, 1AAA, 1BBB and 1CCC, 2,591 mm for the 8 ft 6 in designations 1EE, 1AA, 1BB and 1CC, and 2,438 mm for 1A, 1B, 1C and 1D. Table 3 then gives minima rather than actuals: 2,330 mm minimum internal width for every container, 5,867 mm minimum internal length for a 20 ft and 11,998 mm for a 40 ft, a minimum internal height of the nominal external height less 241 mm, and a minimum door width of 2,286 mm.

ISO 1496-1:2013, the document ISO 668 defers to, does not carry a volume clause either. Its clause 4.2 requires internal dimensions to be “as large as possible” subject to the minima in clause 4.3, and its clause 4.4 sends the rating straight back to ISO 668. So the 33 and 67 and 76 cubic meter figures in universal circulation are carrier and manufacturer figures derived from as-built internal dimensions, and they vary with wall construction, lining and floor thickness.

Rating, tare and payload

Payload is a subtraction, and both of its inputs move. The International Convention for Safe Containers, 1972 defines it in Annex I: maximum permissible payload is “the difference between maximum operating gross mass or rating and tare”, where tare is “the mass of the empty container, including permanently affixed ancillary equipment.”

Rating varies because the fleet spans three generations of the standard. Tare varies with build year, with steel against aluminium construction, with corrugation gauge and floor thickness, with whether the unit carries a gooseneck tunnel or fork pockets, and with repair history, since a box that has had its floor replaced weighs more than its original specification said. The operative figures for a specific shipment are therefore the maximum operating gross mass on that unit’s CSC safety approval plate and the tare painted on its door or rear end, and nothing else. MSC.1/Circ.1475 paragraph 12.1 points at exactly that marking, and CTU Code 6.2.2 repeats it.

Tare is not on the CSC plate. Annex I Regulation 1.2(a) lists what the plate must carry, in English or French: the words CSC SAFETY APPROVAL, the country of approval and approval reference, the month and year of manufacture, the manufacturer’s identification number, the maximum operating gross mass in kilograms and pounds, the allowable stacking load for 1.8 g in kilograms and pounds, and the transverse racking test force in newtons. Tare appears under the ISO 6346:2022 marking rules instead, which is why the two numbers a shipper needs sit in two different places on the same box.

Maximum gross mass: 30,480 kg, 32,500 kg and 36,000 kg

The rating history is three amendments, and quoting the wrong one misstates the ceiling by 5.5 tonnes. ISO 668:1995/Amd 1:2005, published 15 September 2005, raised the 20 ft and 30 ft classes to 30,480 kg, naming them individually: for 1BBB, 1BB, 1B, 1BX, 1CC, 1C and 1CX containers, replace the rating R by 30,480 kg and 67,200 lb. The 40 ft classes already carried that figure.

ISO 668:2013/Amd 2:2016 did not raise the rating. It changed clause 5.2.2 only, permitting a higher value “for particular traffic” up to 36,000 kg where the container is tested and marked to its actual rating, and left Table 2 alone. Table 2 still read 30,480 kg when the seventh edition was published in January 2020. The rating itself became 36,000 kg with ISO 668:2020/Amd 1:2022, published in February 2022, which replaced Table 2 outright with 36,000 kg for every designation except the 10 ft 1D and 1DX at 10,160 kg, and deleted the permissive paragraph that had allowed the exception.

The intermediate step is visible in service. Maersk plates its 40 ft and 45 ft steel dry units at 32,500 kg, a figure above the old Table 2 value and below the 36,000 kg ceiling, which is exactly the 2016 permission being used: a container rated above the table, tested and marked to its actual rating.

The reference table, and which columns are standardized

The standardized columns come from ISO 668:2020 and its 2022 amendment. The capacity, tare and payload columns are Maersk’s published cargo container specifications, accessed 11 September 2026, which that carrier qualifies with the note that dimensions vary with container series. They are one carrier’s representative fleet figures, not values for any given box.

Read the payload column against the common claim that a 20 ft box carries more cargo weight than a 40 ft. On this fleet it does not: 28,300 kg against 28,870 kg, because the 40 ft units are plated 2,020 kg higher and their tare advantage is smaller than that gap. The container ship size classes that carry these boxes price a slot by the box rather than by its contents, and on a container ship the tier above the single unit is the stack. The real reason dense cargo books 20 ft boxes is that a 20 ft reaches its weight ceiling at roughly half the cube, so a heavy, compact cargo fills the weight allowance without paying for volume it cannot use, and it spreads across two road movements with two sets of axles instead of one.

Nominal against usable volume

Published capacity is a ceiling, not a stow. The door aperture is narrower and lower than the section behind it, at a minimum door width of 2,286 mm against a minimum internal width of 2,330 mm, so a load that fits the cube does not always pass the doorway. Pallets do not tessellate against the floor: eleven Euro pallets at 1,200 by 800 mm or ten ISO pallets at 1,200 by 1,000 mm fill a 20 ft floor tier, and 25 Euro or 21 ISO fill a 40 ft, with the gaps between and above them counted in the nominal cube and unusable in a real stow. Those pallet counts are forwarder planning figures, not standard values; no ISO document states them.

dunnage and securing material take more, and the CTU Code constrains how the remainder may be arranged. Annex 7 paragraph 3.1.4 requires the joint centre of gravity of the cargo to sit close to mid-length and mid-width, with eccentricity not exceeding 5 percent in general, given as a rule of thumb as 60 percent of the cargo mass within 50 percent of the container’s length, and up to 10 percent accepted in particular circumstances because modern spreaders can adjust for it. CTU Code 6.2.4 sets the structural envelope behind that: side walls are designed for a uniform load equal to 60 percent of the permitted payload, the front wall and door end for 40 percent, and the floor for the total payload homogeneously distributed.

Special equipment shifts the volume figure again. A reefer container loses internal volume to insulation and to the integral refrigeration unit at one end, so its capacity runs materially below a dry box of the same designation. Flat racks and open tops trade the cube for the ability to carry out-of-gauge pieces that belong with heavy-lift and project cargo . Dangerous goods packed in any of them bring the IMDG Code segregation rules into the stow plan, which can strand capacity that the cube says is available.

Verified gross mass: the SOLAS weighing rule

Since 1 July 2016 a packed container may not be loaded aboard a ship unless its verified gross mass has been determined by the shipper and declared in the shipping document. The requirement sits in SOLAS chapter VI regulation 2, as amended by resolution MSC.380(94), adopted on 21 November 2014 and deemed accepted on 1 January 2016. The full obligation, the national implementations and the documentary chain are covered in verified gross mass and the container weight declaration ; what follows is what a quoting or packing desk needs at the point the box is stuffed.

The rule exists because a planner’s arithmetic is only as good as the weights fed into it. Stowage, intact stability , stack loads and lashing forces are all computed from declared box weights, through the ship’s loading computer and its lashing software , against the cargo securing and lashing systems specified in the cargo securing manual and the CSS Code . A box declared at 18 tonnes that actually weighs 26 puts the error into the stack it sits in and into the twistlocks and securing fittings holding it, which is the mechanism behind stack collapse and a share of the containers lost at sea every year.

Method 1 and Method 2

SOLAS regulation VI/2.4 gives two methods and no third. Method 1 weighs the packed and sealed container on calibrated and certified equipment, in one reading, which is the verified gross mass directly. Method 2 weighs all packages and cargo items, “including the mass of pallets, dunnage and other securing material to be packed in the container”, and adds the container tare, “using a certified method approved by the competent authority of the State in which packing of the container was completed.”

The asymmetry between them is the process approval. Method 1 needs no approval beyond the equipment meeting the accuracy requirements of the State where the weighing is done, which MSC.1/Circ.1475 paragraph 7.1 keys to that State rather than to the flag or the port of loading. Method 2 requires the summing method itself to be certified, and paragraph 5.1.2.3 leaves it to the State of packing to decide whether it certifies the procedure, the party performing it, or both. High-volume packers of known-weight goods usually find Method 2 cheaper per box once the process is approved; a single shipper with mixed cargo takes the box to a weighbridge .

Method 2 is not available for everything. MSC.1/Circ.1475 paragraph 5.1.2.2 states that scrap metal, unbagged grain and other cargo in bulk do not lend themselves to individual weighing, that Method 2 would be inappropriate and impractical for them, and that Method 1 should be used instead. Where an individual original sealed package carries its accurate mass clearly and permanently marked on its surface, paragraph 5.1.2.1 allows it to be taken as read rather than re-weighed.

Weighing on a road vehicle has its own arithmetic. Paragraph 11.1 requires the tare of the vehicle and, where applicable, the tractor to be deducted from their registration documents, along with the mass of fuel in the tractor’s tank. Paragraph 11.2 requires two containers on one vehicle to be weighed separately and states that simply dividing the combined gross mass by two should not be allowed.

The declaration, the signature and the cut-off

Regulation VI/2.5 requires the verified gross mass to be stated in the shipping document, signed by a person duly authorized by the shipper, and submitted to the master or his representative and to the terminal representative sufficiently in advance to be used in preparing the ship stowage plan. The footnote to the regulation accepts presentation by electronic data processing or electronic data interchange, and allows the signature to be electronic or to be replaced by the name of the authorized signatory in capitals.

There is no SOLAS deadline. MSC.1/Circ.1475 paragraph 6.3.2 says so directly: no time deadline is prescribed other than that the information reach the master and the terminal in time for the stowage plan, and it puts the duty on the shipping company to tell the shipper the operational cut-off after discussing it with the terminal. Every VGM cut-off a shipper works to is therefore a commercial term in the booking, not a regulatory one, which matters when a missed cut-off is argued about afterwards.

The obligation rests on the named shipper even where a third party packs the box. Paragraph 5.1.3 keeps it there where several parties pack or supply the cargo, and CTU Code 11.3.3 puts the matching duty on the packer to pass the container identification number, the verified gross mass and the seal number up the chain so they reach the transport document.

What happens without a verified gross mass

Regulation VI/2.6 prohibits loading where the shipping document does not provide the verified gross mass and the master or his representative and the terminal representative have not obtained it. The conjunction is the part that gets misquoted. A container arriving without a declared figure is not automatically stranded: MSC.1/Circ.1475 paragraph 13.1 expressly contemplates the master or the terminal obtaining the verified gross mass on the shipper’s behalf, by weighing in the terminal or elsewhere, with the costs apportioned as the commercial parties agree.

A correct figure is not an entitlement either. Paragraph 14.1 states that availability of the verified gross mass is a prerequisite for loading but does not constitute an entitlement for loading, leaving the master’s discretion intact. And paragraph 10.1 carries the separate limit that a container may not be packed above the maximum gross mass on its CSC plate, under SOLAS regulation VI/5, so a box can be correctly weighed and still refused.

Enforcement sits with the port State. Paragraphs 15.1 and 15.2 make it a matter for SOLAS contracting governments acting under national legislation, with the practical sanction being denial of loading and the costs of non-loading, storage, demurrage or return falling where the contract puts them. In practice a port state control intervention on weight is rare compared with the commercial sanction of a box that does not sail.

Tolerances: what SOLAS says, and what two administrations added

SOLAS regulation VI/2 states no tolerance and MSC.1/Circ.1475 states none. Two administrations published positions, and they are different kinds of instrument.

The United Kingdom Maritime and Coastguard Agency, in MGN 534 (M+F) of June 2015, wrote at paragraph 13.1 that it is anticipated that regulators and other authorised cargo inspectors will use an enforcement threshold of plus or minus 5 percent of the verified gross mass, used on a case by case basis. That is guidance to inspectors about when to intervene, not a margin a shipper may build into a declaration, and the same notice requires misdeclarations to be corrected and recorded. The frequently quoted formulation of plus or minus 5 percent or 500 kg, whichever is greater, does not appear in MGN 534.

The United States published no percentage at all. By marine safety information bulletin 009/16 of 28 April 2016 the Coast Guard determined that existing US laws and regulations for providing verified container weights are equivalent to the SOLAS requirement, naming equipment already used to comply with the Intermodal Safe Container Transportation Act and with the container weight requirements at 29 CFR 1918.85(b) as acceptable. That is an equivalency finding, not a tolerance, and describing it as a US weight tolerance misstates it.

The CTU Code, and what it is not

The IMO, ILO and UNECE Code of Practice for Packing of Cargo Transport Units was issued as MSC.1/Circ.1497 on 16 December 2014, after approval by the Maritime Safety Committee, by the UNECE Inland Transport Committee at its 76th session in February 2014 and by the ILO Governing Body at its 322nd session, and it revoked the earlier MSC/Circ.787. Being a circular, it is not mandatory in its own right. It binds where a mandatory instrument, a contract of carriage, an insurance condition or national law adopts it, which in practice is often. A revision has been in progress at the IMO sub-committee on carriage of cargoes and containers, and the 2014 text remains the operative one.

One document it describes is regularly misunderstood. The container or vehicle packing certificate at CTU Code 11.3.6 is a dangerous goods document, required by SOLAS regulation VII/4.3 , the IMDG Code and other transport regulations where dangerous goods are packed for a route including a maritime leg, certifying that packing was carried out in accordance with those regulations. An ordinary general-cargo container does not carry one.

Road weight limits: the ceiling the box never shows

A container that is legal at sea is frequently illegal on the road, because road weight law caps the whole vehicle combination while the CSC plate rates only the box. This is the limit that actually binds a heavy door-to-door move, and it is set in the jurisdiction of each land leg rather than by any maritime instrument.

In the European Union, Council Directive 96/53/EC as amended by Directive (EU) 2015/719 of 29 April 2015 sets 40 tonnes as the maximum authorised weight for the usual articulated combination in international traffic. Two intermodal derogations raise it: 42 tonnes for a two-axle motor vehicle with a three-axle semi-trailer, and 44 tonnes for a three-axle motor vehicle with a two-axle or three-axle semi-trailer, in each case only where the vehicle is carrying one or more containers or swap bodies up to a total maximum length of 45 feet in an intermodal transport operation. Article 10c allows a 15 cm increase in maximum authorised length and in the king-pin to rear distance for vehicles carrying 45 ft units in such an operation, which is what made the 45 ft box road-legal in the first place. Member States may restrict the derogations on specified parts of their networks.

In the United States the Interstate limits are 80,000 lb gross, 20,000 lb on a single axle and 34,000 lb on a tandem axle, under 23 U.S.C. 127 and 23 CFR 658.17, subject to the bridge formula enacted in 1975. A single axle is one or more axles with centres not more than 40 inches apart, a tandem is two or more consecutive axles with centres more than 40 inches and not more than 96 inches apart, and two consecutive tandems may each carry 34,000 lb where the first and last axles of the group are 36 feet or more apart, which is precisely what makes the standard five-axle tractor-semitrailer legal at 80,000 lb.

The arithmetic is what matters at the packing station. Eighty thousand pounds is 36,287 kg for the whole combination. A tractor and skeletal chassis run roughly 15,000 kg, and a 20 ft container tare is a little over 2,000 kg, so the legal cargo mass on a standard Interstate drayage leg lands near 19,000 kg against a plate rating of 30,480 kg. A shipper who packs to the plate has built a box that cannot legally leave the terminal, and the remedy at that point is to strip and re-stuff across two units, at the cost of a second haulage leg, a second terminal handling charge and a new verified gross mass for each box.

A revision of the EU directive is in progress and has not been adopted. The Commission proposal COM(2023) 445 passed a European Parliament first reading on 12 March 2024 and reached a Council general approach on 4 December 2025, with trilogues opened on 9 December 2025 and no provisional agreement as of 1 August 2026. The proposed intermodal height allowance and the additional tonnage for zero-emission vehicles are proposals. Quoting them as law is the same error as quoting an adjourned IMO measure as adopted.

Stowage factor: the same idea in the bulk trades

The stowage factor is the volume one tonne of a cargo occupies, in cubic meters per tonne, and it is the bulk trade’s version of the divisor. The IMSBC Code defines it in section 1.7 as the figure which expresses the number of cubic meters which one tonne of cargo will occupy, and its section 12 carries the conversion tables between cubic meters per tonne and cubic feet per long ton.

The break-even is the same number in another unit. A cargo with a stowage factor above 1.0 cubic meters per tonne is volume cargo and bills on its measurement under the W/M basis; one below 1.0 is weight cargo and bills on its weight. That is the 1,000 kg per cubic meter line seen from the cargo’s side rather than the tariff’s.

Where the analogy stops is the ship. A bulk carrier’s constraint is the interaction of hold cubic, broken stowage , trim and the cargo intake and deadweight constraints that follow from the lightweight against deadweight split, none of which has an analogue in a parcel tariff. Neither does the ship’s own measured volume: gross tonnage and tonnage measurement describe the enclosed volume of the ship under the Tonnage Convention and have nothing to do with the cube of the cargo inside it, a confusion worth naming because both are quoted in volume-derived units.

Errors, disputes and invoice audit

Five errors account for most of the money lost in this subject, and each has a mechanical fix. They are worth naming individually because each moves a figure by a factor rather than by a margin.

The units error in CBM misstates volume by 10,000 where a centimeter-measured product is divided by 100 instead of 1,000,000. The wrong divisor misprices every light shipment, at 20 percent between the air 6,000 and the express 5,000 and at a factor of six between air and the sea W/M basis. Taking the lesser of the two weights, or quoting the volumetric figure alone on dense cargo, under-bills the carrier and the difference comes back on the correction notice. Planning a container load to published capacity rather than an achieved stow leaves cargo on the dock. And an estimated verified gross mass is not a verified one under either method, which holds the box.

A sixth, specific to air, is compounding the rounding. Multiplying the cube by 167 rather than dividing by 6,000 overstates the chargeable weight at every volume above one cubic meter, and applying the rounding at the piece level rather than at the consignment level overstates it again.

How a carrier re-measures, and what answers it

Carriers audit declared dimensions automatically. Dimensioning gates at hub sortation measure and weigh every piece in transit, and a discrepancy produces a correction notice and a re-billed invoice weeks after delivery, usually with a re-weigh or correction fee attached. The dispute that follows is evidential, and it is won with documents created at packing rather than reconstructed afterwards.

The evidence that works is the dimensioned packing list, photographs of the packed pieces against a measure, the weighbridge ticket or certified scale record, the carrier’s own gate reading where it can be obtained, and the tariff clause that sets the divisor and the rounding rule for the service actually used. The tariff is the operative document, because the divisor is a contract term and not a regulated figure, and a tariff that rounds dimensions down from 0.1 to 0.4 cm produces a different lawful answer from one that rounds every dimension up.

Where the chargeable figure lands downstream

The freight charge this arithmetic produces does not stop at the transport invoice. On a CIF basis it enters the customs value: the WTO Valuation Agreement Article 8.2 leaves each member to decide whether transport and insurance to the place of importation are included, and the European Union includes them under Article 71(1)(e) of Regulation (EU) No 952/2013, with through-freight apportioned in proportion to distance to the place of introduction under Article 138 of Implementing Regulation (EU) 2015/2447. The United States values on an FOB basis, so international freight sits outside the customs value entirely. The consequence is that an overstated chargeable weight on an EU import inflates the duty and the import VAT as well as the freight, which the customs broker declares and the importer of record pays, and which is the build covered in landed cost and import duty and in customs valuation under the WTO agreement , against the duty rate that HS classification fixes.

The same freight figure feeds the insured value. The CIF plus 10 percent convention builds the sum insured from the invoice cost, the freight and the premium, so the freight computed here is a direct input to the cargo insured value . Which party pays it, and which party bears the weighing and declaration cost at each end, is decided by the trade term under Incoterms 2020 , read with the rest of the forwarding chain in freight forwarding and Incoterms .

Putting volume, weight and the box together

The workflow runs in a fixed order: compute CBM, apply the mode divisor, take the greater of the two weights, test the result against a container rate, fit the cargo to the box on the tighter of volume and payload, then verify the gross mass before it can load. Each step consumes the previous one’s output, so an error early is an error everywhere after it.

Take 60 cartons, each 0.6 by 0.4 by 0.4 m, weighing 1,400 kg in total. Each carton is 0.096 CBM and the consignment is 5.76 CBM. By air, the volumetric weight is 5,760,000 divided by 6,000, which is 960.0 kg, below the 1,400 kg actual weight, so air bills 1,400 kg: the cargo is dense at 243 kg per cubic meter, above the 166.67 break-even. By sea on the W/M basis the comparison is 5.76 cubic meters against 1.4 tonnes, so the consignment bills as 5.76 revenue tons, because it is well below 1,000 kg per cubic meter. Same cargo, opposite governing measure, for the reason the break-even densities give.

Scale the same shipper to 600 cartons, 57.6 CBM and 14,000 kg. The LCL bill would now run to 57.6 revenue tons plus the fixed charges, which on any plausible per-revenue-ton rate is far past the crossover, so the cargo goes FCL. It fits a 40 ft box on volume, at 57.6 CBM against the 67.7 cubic meters Maersk publishes, though not comfortably once pallet tessellation and the door aperture are allowed for. On weight it is untroubled: 14,000 kg against a 28,870 kg published payload. The verified gross mass is the cargo plus the pallets, dunnage and securing material plus the container tare, so roughly 14,000 plus 3,630 kg plus the securing material, declared and signed before the carrier’s cut-off.

Change one input and the answer changes shape. At 28 tonnes in the same 57.6 CBM the box still fits on volume and is within the published payload, but a US Interstate drayage leg caps the cargo near 19,000 kg, so the load splits across two 20 ft units, each with its own stuffing, its own road movement and its own verified gross mass. The container never shows that limit. The road law does.

Limitations

The divisors in this article are tariff terms, not regulated constants. The IATA 6,000 sits in the TACT Rules, which are a trade-association publication rather than a regulation, and the express and road figures are carrier tariffs revised annually and quoted here with the dates on which they were published. A specific shipment is governed by the divisor in that carrier’s tariff or in the negotiated rate sheet, and nothing in a general reference overrides it.

Container capacity, tare and payload figures here are one carrier’s published fleet specification, accessed on 11 September 2026, and Maersk qualifies them with the note that dimensions vary with container series. They are not values for any particular box. Internal cubic capacity is not standardized by any body: ISO 668:2020 publishes only minimum internal dimensions and routes the rest to ISO 1496, and ISO 1496-1:2013 gives minima in turn. The operative figures for a shipment are the maximum operating gross mass on that unit’s CSC safety approval plate and the tare marked on its door. Pallet counts per container are forwarder planning figures stated by no standard.

The FCL against LCL crossover is lane-specific and date-specific, and it is computed rather than looked up. No industry constant exists, no public index publishes LCL per-revenue-ton rates, and the commonly quoted 13 to 15 CBM band traces to no tariff, index or survey.

National implementation of the verified gross mass requirement varies in ways this article does not model: equipment accuracy classes are set by the State where the weighing equipment is used, Method 2 certification by the State where packing was completed, and enforcement thresholds by individual administrations, of which the UK and US positions given here are two examples and not a survey. The road weight limits are the EU and US cases only; every other jurisdiction sets its own, and a door-to-door move is capped by the strictest leg.

This article covers standard dry containers and general containerized, air and road cargo. It does not price dangerous goods, out-of-gauge or project cargo, temperature-controlled equipment, tank containers, break-bulk or dry and liquid bulk, each of which is quoted and stowed on a different basis.

Related Articles

• FCL and LCL : the two container load modes compared in their own right, the consolidation chain, and the house and master bill structure behind a groupage booking.
• Chargeable weight : the volumetric billing rule as a standalone term, across the modes that apply it.
• CBM, the cubic meter : the volume unit itself, its conversions, and its relationship to the revenue ton.
• Ocean freight cost and surcharges : how the base rate and the surcharges build the invoice that the chargeable figure here feeds.
• Verified gross mass and container weight declaration : the SOLAS VI/2 obligation in full, with the documentary chain and the national implementations.
• Container ship size classes : the vessels that carry these boxes, and the slot economics one tier up from the single container.
• Landed cost and import duty : where the freight line computed from chargeable weight enters the dutiable value at destination.
• Freight forwarding and Incoterms : the cluster hub one level up, covering the forwarding chain this cost side sits inside.