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. 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. Industry practice is to plan around 85% stuffing efficiency for loose-loaded cartons — which is the threshold this calculator uses. 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%; 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 maxes out around 28 tonnes 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.

The divisors are worth memorising: 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. Typical consumer goods in cartons run 100–150 kg/m³ — almost always volumetric. 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. Some US domestic couriers use inch-based divisors (139 or 166 in³/lb), which land within a few percent of the metric factors.

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 almost 9 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 10 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 comes surprisingly early: on most trade lanes, somewhere around 13–15 CBM an entire 20 ft container (FCL) costs the same as, or less than, shipping that volume LCL. That is well under half the 20 ft box’s ~28 usable CBM. 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: below ~10 CBM, LCL is almost always right. Between 10 and 15 CBM, get quotes for both — the FCL flat rate wins more often than shippers expect. Above 15 CBM, book the 20 ft; above roughly 25–28 CBM, price a 40 ft, whose flat rate is typically only 20–30% above a 20 ft for double the volume. The calculator’s fill bars give you the volume side of this decision instantly; the quotes are the only missing input.