KG to CBM
Convert kilograms to CBM using the sea, road or air volumetric ratio your carrier bills on.
How kg to CBM works
Kilograms measure weight and CBM measures volume, there is no physical formula that turns one into the other, because that depends entirely on what is in the box. What freight modes use instead is a billing convention called a volumetric ratio: an agreed weight that one cubic meter is treated as for chargeable purposes. The three common ratios are:
Sea / LCL: 1 CBM = 1000 kg · Road / LTL: 1 CBM = 333 kg · Air: 1 CBM = 167 kg
To go from kilograms to an implied CBM, divide your weight by the chosen ratio:
CBM = weight in kg ÷ ratio (kg per CBM)
These ratios are conventions, not physics. They exist so a carrier can compare a shipment's actual weight against its volume and bill on whichever is greater. Pick the ratio that matches your mode.
Worked example
A shipment weighs 1200 kg. The implied volume differs by mode:
- Sea: 1200 ÷ 1000 = 1.20 CBM
- Road: 1200 ÷ 333 = 3.60 CBM
- Air: 1200 ÷ 167 = 7.19 CBM
The same 1200 kg looks six times larger by air than by sea, that is the ratio at work, not a change in the goods.
Volumetric ratios
| Mode | 1 CBM is billed as | kg → CBM divide by |
|---|---|---|
| Sea / LCL | 1000 kg | 1000 |
| Road / LTL | 333 kg | 333 |
| Air | 167 kg | 167 |
These are billing conventions, not a measurement of your cargo. Always confirm the exact ratio your carrier or forwarder applies, as some use 6000 cm³/kg air or other house rules.
To reverse the calculation, use CBM to kg. If you actually know the box dimensions, the CBM calculator gives true volume directly, and what is CBM explains how these ratios feed into chargeable weight.