CBM & Chargeable Weight Explained
How CBM, volumetric weight, container utilisation and chargeable weight actually work - for sea LCL, sea FCL, air freight (IATA) and integrator services. With worked examples.
CBM - cubic meters - is the primary volume unit in international freight. It drives ocean LCL rates, container utilisation, and appears on every packing list and B/L. But CBM alone is rarely what you're actually charged for. Chargeable weight is.
Calculating CBM
The formula is simple. The unit trap is not.
- From meters:
CBM = Length × Width × Height(all in m). - From centimeters:
CBM = (L × W × H) ÷ 1,000,000. - From inches:
CBM = (L × W × H) ÷ 61,024(1 inch = 2.54 cm; 2.54³ ≈ 16.387; 1,000,000 ÷ 16.387 ≈ 61,024). - From cubic feet:
CBM = CBF × 0.02832(1 CBF = 0.02832 CBM).
Worked example. A carton measures 120 × 80 × 100 cm.
Volume = 120 × 80 × 100 = 960,000 cm³ ÷ 1,000,000 = 0.96 CBM.
Ocean LCL - the W/M rule
LCL (Less than Container Load) shippers charge on the higher of actual weight and CBM under the weight-or-measure (W/M) rule: 1 CBM of cargo is treated equivalent to 1,000 kg. A 2 CBM shipment weighing 500 kg pays on 2 chargeable tons. A 0.5 CBM shipment weighing 800 kg pays on 0.8 chargeable tons.
So the practical chargeable unit for LCL is max(CBM, weight_kg / 1000). All-in LCL rates in 2026 typically sit at USD 25–65 per chargeable ton on East–West trade lanes, plus origin and destination CFS charges.
Ocean FCL - utilisation, not chargeable weight
FCL (Full Container Load) is a flat rate per container. What matters is utilisation: how much of the box you actually filled.
| Container | Internal CBM | Typical utilisation | Max payload |
|---|---|---|---|
| 20ft dry standard | ~33 CBM | 25–28 CBM | ~28,180 kg |
| 40ft dry standard | ~67 CBM | 54–58 CBM | ~26,700 kg |
| 40ft high-cube | ~76 CBM | 62–66 CBM | ~26,600 kg |
| 45ft high-cube | ~86 CBM | 70–75 CBM | ~26,600 kg |
Utilisation is lower than internal capacity because cartons don't tessellate perfectly and you leave gaps for stability and stripping access. The CBM & Container Calculator takes carton dimensions and gives you actual utilisation percentage.
Air freight - the volumetric divisor
Air cargo charges the higher of actual weight (kg) and volumetric weight:
- IATA general cargo (Res. 502):
Vol. wt. = (L × W × H in cm) ÷ 6000. - Integrator premium (DHL / FedEx / UPS):
÷ 5000. - Some regional carriers use ÷ 4800 or ÷ 4166 on specific lanes.
Worked example. A pallet measures 120 × 80 × 100 cm and weighs 200 kg. Volumetric = (120 × 80 × 100) ÷ 6000 = 160 kg. Since actual (200) > volumetric (160), chargeable weight is 200 kg. On the same dimensions at 100 kg actual, chargeable would be 160 kg.
Chargeable weight is rounded up to the nearest 0.5 kg per piece (or per shipment on a direct AWB). Airlines have rate breaks at +45, +100, +300, +500 and +1000 kg - a lower rate at a higher break can beat the higher rate at your actual weight. It sometimes pays to declare higher to hit the next break.
LCL vs FCL - the break-even
At some CBM count, an FCL container's flat rate becomes cheaper than the per-CBM LCL rate. For a 20ft, that's typically 12–14 CBM. For a 40ft, 26–28 CBM. But the exact crossover depends on:
- All-in LCL rate per chargeable ton (origin + freight + destination).
- FCL flat rate and any surcharges (BAF, LSS, CAF, PSS).
- CFS handling charges (included in LCL, avoided in FCL).
- Free-time and demurrage risk (usually more generous on FCL).
Feed your actual quotes into the LCL vs FCL Break-Even tool for a precise crossover.
Demurrage and detention
Once the container reaches the discharge terminal, free-time starts. Free-time varies by carrier and port but is typically 5–14 days.
- Demurrage - charged when a loaded container overstays free-time at the terminal.
- Detention - charged when the container itself is held outside the terminal (e.g. at the consignee's yard being unloaded).
Rates are tiered and escalating. A typical structure on the US East Coast in 2026:
- Days 1–3 past free-time: USD 100/day.
- Days 4–7: USD 200/day.
- Days 8+: USD 400/day.
Some carriers pool demurrage and detention into a combined "merchant" free-time; others keep them separate. The Detention & Demurrage Calculator supports both structures.
Practical tips
- Weigh every carton. Volumetric-heavy cargo (foam, textiles, furniture) is often 3–5× actual weight on air, and a full 40ft hits volume limits well before weight limits.
- Standardise carton sizes to your pallet footprint (usually EUR 1.2 × 0.8 m or ISO 1.2 × 1.0 m) - utilisation rises 10–20%.
- On air freight, if actual weight is close to a rate break, declaring higher (to the next break) can be cheaper.
- On LCL, watch for consolidator "profit split" surcharges - some apply a min-charge of 1 chargeable ton per B/L.