What is CBM?
CBM (cubic metre) is the standard unit of measurement used in international freight and shipping to calculate the volume of cargo. One cubic metre equals the volume of a cube with 1-metre sides — roughly the size of a large household appliance box.
Freight forwarders, shipping lines, and logistics companies use CBM to determine how much space your goods will occupy in a container or on a ship. It is the basis for LCL (less-than-container-load) pricing, where you pay per cubic metre alongside weight.
Understanding your shipment's CBM helps you compare quotes accurately, avoid surprise costs, and choose the right container size for FCL (full-container-load) bookings.
How CBM is calculated
The formula for a single box is:
\`\`\` CBM per box = Length (m) × Width (m) × Height (m) Total CBM = CBM per box × Quantity \`\`\`
If your dimensions are in centimetres, divide each measurement by 100 to convert to metres before multiplying. If they are in inches, multiply each by 0.0254.
**Example:** 10 boxes each measuring 60 cm × 40 cm × 30 cm - Convert: 0.60 m × 0.40 m × 0.30 m = 0.072 CBM per box - Total: 0.072 × 10 = 0.72 CBM
Standard shipping container capacities
Standard container usable volumes:
- **20ft container** — approximately 33 CBM usable; max payload ~28,000 kg - **40ft container** — approximately 67 CBM usable; max payload ~26,500 kg - **40ft High Cube (HC) container** — approximately 76 CBM usable; max payload ~26,500 kg
Note that stated capacities are theoretical maximums. In practice, irregular cargo shapes, pallets, and dunnage reduce usable space. Always allow a 10–15% buffer and confirm exact dimensions with your freight forwarder.
LCL vs FCL shipping
- **LCL (Less than Container Load):** Your cargo shares a container with other shipments. You are charged per CBM (or per tonne if heavier). Economical for small shipments under ~15 CBM. - **FCL (Full Container Load):** You rent the entire container. More cost-effective for shipments over ~15 CBM, and cargo is not co-loaded with strangers' goods.
The break-even point varies by trade lane, but roughly: if your shipment exceeds half of a 20ft container, getting FCL quotes makes sense.
How to use
1. Select your dimension unit — centimetres or inches 2. Enter the length, width, and height of your first box type 3. Enter the quantity of that box type 4. Click "Add Box Type" to add more box sizes if your shipment has mixed packaging 5. Click "Calculate CBM" to see total volume and container requirements 6. Review the container breakdown to see how many 20ft, 40ft, or 40ft HC containers your shipment needs
FAQs
Q: What does CBM stand for? A: CBM stands for cubic metre (also written m³). It is the universal measurement unit for freight volume in international shipping.
Q: How do I convert inches to CBM? A: Multiply each dimension in inches by 0.0254 to get metres, then multiply length × width × height. The calculator does this automatically when you select inches.
Q: Why does the container percentage shown seem low? A: The percentage shows how full the container would be at 100% theoretical capacity. In practice, not all space is usable due to cargo shapes, pallets, and stacking restrictions. A 70–80% fill rate is often considered efficient.
Q: Can I mix different box sizes? A: Yes. Click "Add Box Type" to add as many different box dimensions as you need. The calculator totals the CBM across all types.
Q: What if my cargo is heavier than the weight limit? A: CBM only measures volume. If your cargo density means the weight limit is reached before the volume limit, you will need more containers than the volume alone suggests. Always check weight limits with your freight forwarder.