CBM Calculator

CBM is nothing more than volume expressed in cubic metres: CBM = length (m) × width (m) × height (m) × quantity. The only mistake people make is a units one — measure in centimetres and forget to divide by 100, and the result is off by a factor of a million.

Worked example, the classic export carton: 60 × 40 × 40 cm. Convert to metres first: 0.6 × 0.4 × 0.4. Multiply: 0.6 × 0.4 = 0.24, then × 0.4 = 0.096 m³ per carton. Ship 100 of them: 0.096 × 100 = 9.6 CBM. In imperial units that is 9.6 × 35.3147 ≈ 339 cubic feet.

Working in inches? The calculator converts for you, but the manual route is: multiply the three dimensions in inches, then divide by 61,024 to get cubic metres (or divide by 1,728 for cubic feet and multiply by 0.0283). A 24 × 16 × 16 in carton works out to 6,144 in³ ÷ 61,024 ≈ 0.1 CBM — almost exactly the same box as the metric example.

If your cartons come in several sizes, run each size separately and add the results — CBM values sum directly. For irregular items (furniture, machinery), measure the smallest rectangular box the item would fit inside; carriers charge for the space the item blocks, not for its actual shape. Boxes packed on pallets should be measured as the loaded pallet: footprint × total height including the pallet itself, since that is the volume that occupies the container. For pallet counts rather than volume, use the pallet calculator.

The bars compare your total CBM against the geometric capacity of each container: 33.2 m³ for a 20 ft, 67.7 m³ for a 40 ft, 76.4 m³ for a 40 ft high cube and 86 m³ for a 45 ft high cube, as the published line and maker sheets print them. A bar past 100% turns red — that cargo physically cannot fit.

The recommendation is stricter than the bars, and deliberately so. No real container is ever stuffed to 100% of its geometric volume: cartons don’t tile the corrugated walls perfectly, door clearance eats space, mixed carton sizes leave voids, and loaders need room to work. This calculator plans around 85% stuffing efficiency for loose-loaded cartons — a rule of thumb, not a measured figure. Your 9.6 CBM example fills a 20 ft container to 29% of geometric capacity, comfortably inside its ~28 m³ of practical space, so the tool recommends the 20 ft.

A shipment that computes to, say, 31 CBM looks like it fits a 20 ft on paper (33.2 m³), but at 93% of geometric volume it almost certainly will not go in — the calculator will correctly push you to a 40 ft. Uniform, palletised or professionally-planned loads can beat 85%, and a container load calculator gives the real count carton by carton; awkward mixed cargo can fall short of it. Treat the recommendation as the safe default, not a law of physics.

Volume is only half the constraint. A 20 ft container is rated for 28,250 kg (62,281 lb) of payload — dense cargo like tiles or paper hits the weight ceiling long before the volume one. Check your totals against the container weight guide.

Carriers sell a fixed amount of space and a fixed amount of lifting capacity, so every mode protects itself against light-but-bulky cargo with a volumetric (dimensional) weight: your volume converted into an equivalent weight using a DIM factor. The chargeable weight — what appears on the invoice — is whichever is greater: actual weight or volumetric weight. Enter a per-item weight above and the calculator runs this comparison for all three modes at once.

Same 9.6 CBM example: by sea LCL the volumetric weight is 9.6 × 1,000 = 9,600 kg — in practice ocean LCL is simply priced per CBM, and only very dense cargo (over 1 t/m³) gets charged by weight instead. By air, 9,600,000 cm³ ÷ 6,000 = 1,600 kg. By courier, 9,600,000 ÷ 5,000 = 1,920 kg. If the 100 cartons actually weigh 12 kg each (1,200 kg total), air and courier both bill the volumetric figure, not the scale weight — you would pay for 1,600 or 1,920 kg of a shipment that weighs 1,200 kg. That gap is exactly why bulky goods travel by sea.

These are the usual divisors, not a rule every carrier follows: a carrier’s own tariff decides. Air’s 1:6000 factor means anything lighter than 167 kg/m³ is charged by volume; couriers’ 1:5000 sets the bar at 200 kg/m³, so light consumer goods in cartons are usually billed by volume. A few carriers quote the same rules differently: you may see air freight expressed as “167 kg per CBM” and courier DIM weight computed per package in cm³ ÷ 5,000 — both produce the numbers in this calculator’s table. US domestic rates can use inch-based divisors: the US Postal Service divides cubic inches by 139 for a rectangular parcel and by 166 for an irregular one, within one percent of 1:5000 and 1:6000.

Spec-sheet capacity and plannable capacity are different numbers. The table below pairs each container’s geometric internal volume with the volume you should actually plan to load at 85% stuffing efficiency — the same figures the recommendation uses.

Note how the 40 ft high cube earns its popularity: one extra foot of height adds 8.7 CBM of geometric volume — roughly 7 more usable CBM — on the same footprint, usually for a small premium over a standard 40 ft. The 45 ft high cube adds another 9.6 m³ on top of that, though it is less common on many trade lanes and can carry inland-haulage surcharges. For the full breakdown of how internal volume is derived from internal dimensions, see the container CBM guide.

Where your shipment lands in this table depends on cargo shape as much as size: tall cargo that cannot be double-stacked wastes the upper half of the box and can push an on-paper 20 ft load into a 40 ft; conversely, uniform cartons that stack floor-to-ceiling get closer to the geometric maximum than the 85% rule assumes.

LCL (less than container load) pricing is per CBM — you share a container with other shippers and pay for the slice you occupy. FCL (full container load) is a flat price for the whole box, whether you fill it or not. Because LCL carries extra handling — consolidation, deconsolidation, per-CBM warehouse fees at both ends — its per-cube rate is much higher than FCL’s effective rate.

The crossover sits where the LCL bill for your volume reaches the price of one whole 20 ft: the 20 ft’s rate with its charges, less the LCL fixed charges, divided by the LCL rate per CBM. Your quotes set that point, not a fixed volume, and the LCL vs FCL calculator works it out from them. Above the breakeven you get the whole container for less money, plus real side benefits: no co-loaders touching your cargo, fewer handling steps and damage points, no waiting for the consolidation to fill, and a simpler customs file.

Practical decision rule: well below the crossover, LCL is almost always right. Near it, get quotes for both — the FCL flat rate wins more often than shippers expect. Above it, book the 20 ft; once the cargo nears the 20 ft’s ~28 usable CBM, price a 40 ft as well, which holds about twice the volume (67.7 m³ against 33.2 m³). The calculator’s fill bars give you the volume side of this decision instantly; the quotes are the only missing input.