CBM Calculator & Chargeable Weight
Calculate CBM, total weight, and IATA chargeable weight for air and sea freight. Optimized for freight forwarders and exporters.
CBM (cubic metre) is the standard unit of volume for sea freight. One CBM equals a box measuring 1 m × 1 m × 1 m. Carriers charge on whichever is greater - actual weight or volumetric weight - so calculating CBM accurately is the first step in getting an honest freight quote.
For air freight, use the IATA divisor of 6,000: divide L × W × H (cm) by 6,000 to get the volumetric weight in kg. For sea LCL, 1 CBM = 1 revenue tonne (W/M - weight or measure, whichever is higher). Use this calculator to check whether your cargo pays on weight or volume, and whether it fits a 20ft or 40ft container.
CBM and chargeable weight formulas
- CBM = L(m) x W(m) x H(m) x pieces. From cm: L x W x H / 1,000,000.
- Air, IATA airlines: volumetric kg = L x W x H (cm) / 6,000.
- Air, express integrators: volumetric kg = L x W x H (cm) / 5,000.
- Chargeable weight = max(actual weight, volumetric weight).
- Sea LCL: 1 CBM = 1,000 kg = 1 revenue tonne (W/M, whichever is greater).
- LCL to FCL breakpoint: about 13 to 15 CBM for a 20ft, 26 to 28 CBM for a 40ft.
| Example shipment | Volume | Actual weight | Charged on |
|---|---|---|---|
| Air, 10 cartons 60 x 40 x 40 cm, 12 kg each (divisor 6,000) | 0.960 CBM | 120 kg | 160 kg volumetric |
| Air, same cartons on an express divisor of 5,000 | 0.960 CBM | 120 kg | 192 kg volumetric |
| Sea LCL, 8 pallets 120 x 100 x 150 cm, 400 kg each | 14.400 CBM | 3,200 kg | 14.4 W/M, past the 20ft FCL breakpoint |
Last reviewed against IATA TACT rules and standard NVOCC LCL tariffs, September 2026.
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Overview & methodology
CBM formula for container stuffing
CBM = length (m) × width (m) × height (m) × quantity
For a 40ft High Cube the geometric internal volume is about 76.3 CBM (12.03 × 2.35 × 2.70 m). Practically usable stowage is roughly 65 to 70 CBM once pallets, dunnage and cargo geometry are allowed for, which is why this calculator plans on 67.7 CBM.
Container internal dimensions and capacity
| Container | Internal length | Internal width | Internal height | Geometric internal volume (CBM) | Planning capacity used here (CBM) | Max payload |
|---|---|---|---|---|---|---|
| 20ft Standard | 5.89 m | 2.35 m | 2.38 m | 32.9 | 25.5 | 28,000 kg |
| 40ft Standard | 12.03 m | 2.35 m | 2.38 m | 67.3 | 55.0 | 28,500 kg |
| 40ft High Cube | 12.03 m | 2.35 m | 2.70 m | 76.3 | 67.7 | 28,500 kg |
| 20ft Reefer | 5.44 m | 2.27 m | 2.27 m | 28.0 | 28.0 | 27,400 kg |
| 40ft HC Reefer | 11.58 m | 2.29 m | 2.50 m | 66.3 | 67.5 | 29,000 kg |
| 20ft Open Top | 5.89 m | 2.35 m | 2.38 m | 32.9 | 32.5 | 28,080 kg |
Geometric volume is length × width × height of the empty box. Planning capacity is the realistic stowage this calculator uses. Dimensions vary slightly by carrier and container build; check your carrier's specification.
How to calculate CBM from dimensions
CBM = Length (m) × Width (m) × Height (m). If your dimensions are in centimetres, divide by 1,000,000: a carton of 120 × 80 × 100 cm = 0.96 CBM. For multiple pieces, multiply one carton's CBM by the piece count.
The W/M rule for sea LCL means you pay the higher of actual weight (per tonne) or volume (per CBM). If your cargo weighs 0.5 t but occupies 1.2 CBM, you pay on 1.2 revenue tonnes. Use the LCL/FCL breakeven tool to find the container tipping point.
Air freight chargeable weight: IATA vs integrator divisors
Airlines use 6,000 cm³/kg (IATA standard). Express integrators (DHL, FedEx, UPS) often use 5,000 cm³/kg on premium products, meaning the same box pays more. Always confirm the divisor on the quotation.
Numerical Example: Air Freight Chargeable Weight Calculation
Volumetric weight (167 kg) exceeds actual weight (100 kg) - the airline bills on 167 kg. This is typical for lightweight, bulky consumer goods.
Container utilisation and break-even
A 20ft standard container has ~33 CBM internal capacity; usable load is 25–28 CBM once cartons are stacked. The typical LCL-to-FCL switch point is around 12–14 CBM for a 20ft, but it depends on your specific LCL rate vs. FCL flat cost. See the LCL vs FCL break-even calculator for the full analysis.
Method note: calculations run in your browser using the formulas and published rule books cited on this page. Results are free estimates for planning, with no login required, and should be confirmed with your bank, broker or the official source before you commit.
Frequently asked questions
How do I calculate CBM?
Multiply length x width x height in metres, then by the number of pieces. From centimetres, divide L x W x H by 1,000,000. A 120 x 100 x 150 cm pallet is 1.8 CBM.
How is air freight chargeable weight calculated?
Volumetric weight = L x W x H (cm) / 6,000 for IATA airlines, or / 5,000 for most express integrators. Chargeable weight is whichever is greater: actual gross weight or volumetric weight.
What does W/M mean in sea LCL freight?
Weight or measure. 1 CBM is treated as 1,000 kg (one revenue tonne), and the carrier charges on whichever is higher: cubic metres or metric tonnes.
When is FCL cheaper than LCL?
Roughly from 13 to 15 CBM for a 20ft container and 26 to 28 CBM for a 40ft, although the exact breakpoint depends on current LCL and FCL rates on your lane.
Why is the IATA divisor 6,000 but express uses 5,000?
A smaller divisor produces a higher volumetric weight. Express couriers use 5,000 because light, bulky parcels take up aircraft space disproportionately; general air cargo uses the IATA 6,000 standard (1 CBM = 166.67 kg).