CBM is length × width × height in metres. A 60 × 40 × 50 cm carton is 0.6 × 0.4 × 0.5 = 0.12 CBM, and 20 of them are 2.4 CBM. In centimetres, divide L × W × H by 1,000,000; in inches, divide by 61,024.
Add a line for each carton size in your shipment. The calculator totals the CBM and weight, shows the share of a 20 ft, 40 ft and 40 ft high cube container, and gives the volumetric and chargeable weight for courier or air.
How to calculate CBM
| Measured in | Formula for one carton | Example |
|---|---|---|
| Centimetres | L × W × H ÷ 1,000,000 | 60 × 40 × 50 ÷ 1,000,000 = 0.12 |
| Millimetres | L × W × H ÷ 1,000,000,000 | 600 × 400 × 500 ÷ 10⁹ = 0.12 |
| Inches | L × W × H ÷ 61,024 | 24 × 16 × 20 ÷ 61,024 = 0.1259 |
| Feet | L × W × H ÷ 35.315 | 2 × 2 × 2 ÷ 35.315 = 0.2265 |
| Metres | L × W × H | 0.6 × 0.4 × 0.5 = 0.12 |
Then multiply by the number of cartons. For a mixed shipment, work out each size separately and add them up. Measure the outside of the carton, including any bulge, because that is what the forwarder measures.
Example shipment: 20 cartons of 60 × 40 × 50 cm (2.4 CBM) and 10 cartons of 45 × 35 × 30 cm (0.4725 CBM) make 2.8725 CBM, or about 101.4 cubic feet.
Container sizes
Inside measurements and capacities are from a major shipping line's equipment specifications. Other lines' boxes differ by a few centimetres.
| Container | Inside size | Capacity | Planning figure (85%) | Max cargo weight |
|---|---|---|---|---|
| 20 ft standard | 5.90 x 2.35 x 2.39 m | 33 CBM | 28.1 CBM | 28,200 kg |
| 40 ft standard | 12.03 x 2.35 x 2.39 m | 67 CBM | 57.0 CBM | 28,800 kg |
| 40 ft high cube | 12.03 x 2.35 x 2.70 m | 76 CBM | 64.6 CBM | 28,620 kg |
Cartons of different sizes, pallets and gaps for air mean a container never loads to 100%. We use 85% of the inside volume as a planning figure. A 20 ft container at 85% holds about 28 CBM, which is roughly 233 cartons of 0.12 CBM, if the weight allows. Your forwarder's load plan is the final word.
Volumetric and chargeable weight
Couriers and airlines charge for space as well as weight. They work out a volumetric weight and bill whichever is higher, the actual weight or the volumetric weight. That higher figure is the chargeable weight.
Volumetric weight (kg) = L × W × H in cm ÷ divisor
- 5000 is used by express couriers. DHL Express publishes this divisor.
- 6000 is the standard for air cargo set by IATA, used by most airlines and air freight forwarders.
One 60 × 40 × 50 cm carton is 120,000 ÷ 5000 = 24 kg by courier, or 120,000 ÷ 6000 = 20 kg as air cargo. If it actually weighs 18 kg, you pay for 24 kg or 20 kg. Divisors and rounding rules differ between companies and change, so confirm with the courier you book.
For sea freight in a shared container (LCL), forwarders commonly charge per CBM or per 1,000 kg, whichever is more. The calculator shows this as billing units.
Tips to lower the chargeable figure
- Use the smallest carton that protects the goods. Cutting 5 cm off each side of a 60 × 40 × 50 carton takes it from 0.12 to about 0.087 CBM, nearly 28% less.
- Pack light, bulky goods such as garments, pillows or plastic items in compressed or vacuum bags.
- Mixed cargo: put heavy and light cartons in the same air shipment so the actual weight rises closer to the volumetric weight you pay for anyway.
- For sea freight, once a shipment nears half a container, ask for both an LCL price and a full 20 ft container price.
CBM questions
How do I calculate CBM of a carton in inches?
Multiply length, width and height in inches, then divide by 61,024. A 24 × 16 × 20 inch carton is 7,680 cubic inches, and 7,680 ÷ 61,024 = 0.126 CBM. Or convert each side to metres first by multiplying by 0.0254.
How many CBM is a 20 ft container?
About 33 CBM inside. In practice you can load about 25 to 28 CBM of cartons, depending on carton sizes and how well they stack. A 40 ft container is about 67 CBM inside and a 40 ft high cube about 76 CBM.
How do I convert CBM to cubic feet?
Multiply by 35.315. So 1 CBM is 35.315 cubic feet, and 2.4 CBM is about 84.8 cubic feet. To go from cubic feet to CBM, divide by 35.315.
What is chargeable weight?
The weight you are billed for: the higher of the actual weight and the volumetric weight. A 10 kg box that measures 50 × 50 × 50 cm has a volumetric weight of 25 kg at a 5000 divisor, so you pay for 25 kg.
Can I convert CBM to kg?
Not directly, because CBM is space and kg is weight. What you can do is find the volumetric weight: 1 CBM equals 200 kg at a 5000 divisor and about 167 kg at 6000. For sea freight, forwarders commonly treat 1 CBM as 1,000 kg for billing.
Last reviewed 30 September 2026. Results are estimates; official notices always take precedence.