CBM: The Complete Calculation Guide (With the Traps)
CBM — cubic meters — is the currency of ocean freight. LCL rates quote per CBM, container decisions count CBM, and your forwarder's math starts from it. It's also where measurement mistakes and rounding traps quietly live. The complete guide:
The basic formula
- •Per carton: CBM = Length × Width × Height (cm) ÷ 1,000,000
- •Shipment total: carton CBM × quantity
- •Example: 60 × 40 × 40 cm = 96,000 cm³ ÷ 1,000,000 = 0.096 CBM per carton
- •200 cartons: 0.096 × 200 = 19.2 CBM total
The traps we see weekly
- •Measuring the product, not the carton — bulges, handles and pallets count
- •Factory-stated dimensions that flatter by 2–3 cm per side (volume error compounds cubically)
- •LCL's 'minimum chargeable volume' — often 1 CBM even if you ship 0.4
- •Weight-ratio billing: some lanes bill the higher of CBM or weight ÷ 1,000 (1 ton per CBM)
How much fits, really
Container capacity is geometry, not spec sheets: usable space always runs below the theoretical maximum once you account for carton shapes, stacking patterns and loading access.
- •20ft GP: nominal 33 CBM — realistically ~28 CBM of cartons
- •40ft GP: nominal 67 CBM — realistically ~58 CBM
- •40ft HQ: nominal 76 CBM — realistically ~66 CBM
- •Weight limits cap you first on dense cargo: 20ft ≈ 21–22 tons payload
The decision CBM drives
Under ~10 CBM, LCL usually wins. Between 10–15, model both modes — the crossover is cargo-specific and destination-fee-dependent (that $30–60/CBM CFS charge moves it). Above 15, the container is almost always right. Run your numbers in the homepage calculator — it applies all three rules automatically, including the crossover warning.