What Is CBM and How to Calculate It
CBM means cubic meter, length × width × height measured in meters. Here is the formula, worked examples, and how CBM is used in freight.
What CBM means
CBM stands for cubic meter (written m³). It is the volume a box or shipment occupies, measured with every dimension in meters. One CBM is a cube one meter on each side. It is the single most-used figure in freight planning because, unlike weight or load configuration, it never changes with carrier, route or season, it is fixed geometry.
The formula is straightforward:
CBM = length (m) × width (m) × height (m)
If your dimensions are in centimeters, inches or feet, convert each side to meters first, then multiply. The most common slip is mixing units, measuring in centimeters but treating the answer as if it were already in meters.
How to calculate CBM, step by step
- Measure the length, width and height of one carton.
- Convert each measurement to meters.
- Multiply the three together for the CBM of one carton.
- Multiply by the number of identical cartons for the shipment total.
Worked example. A carton measures 120 × 100 × 90 cm. Convert: 1.2 m × 1.0 m × 0.9 m = 1.08 CBM per carton. In cubic feet that is 1.08 × 35.3147 = 38.14 ft³. For 15 such cartons the shipment is 15 × 1.08 = 16.2 CBM.
A quick check when you are in centimeters: multiply the three sides and divide by 1,000,000. Here 120 × 100 × 90 = 1,080,000 cm³ ÷ 1,000,000 = 1.08 CBM, the same result. You can run any of these on the CBM calculator, and for a load of several carton sizes use the CBM calculator for multiple boxes.
CBM conversions worth knowing
| Conversion | Factor |
|---|---|
| 1 CBM | 35.3147 ft³ |
| 1 ft³ | 0.0283168 m³ |
| 1 CBM | 1000 litres |
| 1 m | 100 cm = 1000 mm |
| 1 in | 0.0254 m |
| 1 ft | 0.3048 m |
How CBM is used in freight
CBM is the space measure that freight modes plan around, and each mode also uses a volumetric ratio, a billing convention that converts volume into an equivalent weight so that light, bulky cargo is not under-counted. These are conventions, not physics:
| Mode | Convention |
|---|---|
| Sea / LCL | 1 CBM = 1000 kg |
| Road / LTL | 1 CBM = 333 kg |
| Air | 1 CBM = 167 kg |
For example, the 16.2 CBM shipment above would be treated as roughly 16,200 kg of "volume weight" on a sea LCL basis, against which the actual weight is compared. The same idea at the parcel scale is dimensional weight, covered in dimensional weight explained, where a divisor turns a box's cube into a billable weight.
A few limits to keep in mind:
- CBM is carton cube only. It does not include pallet bases, stacking gaps, or the void space left when boxes do not perfectly fill a container.
- Real space used is always higher than raw CBM. Plan actual loading with a tool that models the interior, such as the container load calculator.
- Volumetric ratios are billing conventions, not the weight of the goods. They exist to account for space fairly, and the exact figures can vary by carrier.
If you only need the plain volume of a box in m³, ft³ and litres without the freight framing, the box volume calculator gives exactly that. Either way the core idea is the same: measure in meters, multiply three sides, and you have CBM.