A Visual Guide to CBM Calculation

CBM — Cubic Meter — is the single most important number on any ocean or air freight quote. It tells the carrier how much space your cargo will occupy, and it's how forwarders bill you for LCL shipments. The math is simple, but importers still get it wrong because of unit mismatches and forgetting to multiply by the carton count. This visual guide walks through it the right way.

1. The core formula

Every CBM calculation starts with one carton and three measurements: Length, Width, and Height. Multiply them together and you have the volume of that carton in cubic meters — provided every measurement is in meters first.

Example: a carton measuring 0.6 m × 0.4 m × 0.5 m has a CBM of 0.6 × 0.4 × 0.5 = 0.12 CBM.

2. Convert units before you multiply

90% of CBM mistakes are unit mistakes. Suppliers in China usually quote in centimeters, US warehouses in inches, and European freight quotes in meters. Convert everything to meters before you apply the formula.

• Centimeters → meters: divide by 100. (60 cm ÷ 100 = 0.6 m)
• Inches → meters: multiply by 0.0254. (24 in × 0.0254 = 0.6096 m)
• Feet → meters: multiply by 0.3048.

If you don't want to do the math by hand, the Shipping Unit Converter handles every direction in one click.

3. Multiply by the number of cartons

A single carton's CBM is almost never what the forwarder needs. They need the total shipment volume — single carton CBM × total carton count.

Example: 10 cartons of 0.5 CBM each = 5 CBM total. If your shipment has multiple SKUs in different carton sizes, calculate each SKU separately and sum the results.

Worked example, end-to-end

• SKU A: 50 cartons at 55 × 40 × 30 cm = 50 × (0.55 × 0.40 × 0.30) = 3.30 CBM
• SKU B: 30 cartons at 60 × 45 × 35 cm = 30 × (0.60 × 0.45 × 0.35) = 2.835 CBM
• Shipment total: 6.135 CBM — below the typical 15 CBM LCL/FCL breakeven, so LCL wins.

4. When CBM isn't the chargeable number

For air freight, carriers compare actual weight against volumetric weight and bill on whichever is higher. The IATA divisor is 6000 (cm³ ÷ 6000 = volumetric kg). For light bulky cargo — pillows, lampshades, foam — volumetric weight almost always wins, so CBM alone understates cost.

Use the Volumetric Weight Calculator to see your chargeable weight before booking air.

5. From CBM to container choice

Once you have a total CBM, container choice is mostly arithmetic. Standard usable capacities (loadable, not theoretical) are roughly:

• 20ft: ~28 CBM loadable
• 40ft: ~58 CBM loadable
• 40HC: ~68 CBM loadable

Drop your numbers into the Container Capacity Calculator and it picks the right box for you.