What is CBM, and how sea freight is actually priced

Sea freight quotes are in CBM — cubic meters — and most billing surprises trace back to not understanding how that number is computed. Five minutes here saves you from every one of them.

The formula

CBM is just the space your cartons occupy:

Worked example: your supplier packs your order into 8 cartons of 60 × 50 × 40 cm. One carton is 60 × 50 × 40 = 120,000 cm³ ÷ 1,000,000 = 0.12 CBM. Eight cartons = 0.96 CBM. At an all-in rate quoted per CBM, that number times the rate is your shipping cost — taxes, port fees and warehouse fees included when the rate is genuinely all-in.

Ask your supplier for the carton dimensions and count before the goods ship — they have this on the packing list. You can then run the numbers in our shipping calculator instead of discovering the cost when the bill arrives.

Volume or weight — whichever is greater

Here is the part that surprises people: sea freight is billed on volume or weight, whichever costs more. Every forwarder sets a weight allowance per CBM; ours is generous by industry standards — see the current figure in our published rates, along with the per-kilo charge that applies beyond it. Ship a cubic meter of throw pillows and you pay for 1 CBM of space. Ship a cubic meter of steel hinges and the weight, not the volume, sets the bill.

This is why the same 0.96 CBM can cost two importers different amounts, and why "how much per CBM?" is only half a quote. When comparing forwarders, always ask for the weight allowance and the excess rate — a suspiciously low per-CBM price with a stingy allowance is a quote designed to grow after your cargo is in their custody. (A rate that seems impossibly cheap is worth a legit check before it is worth a booking.)

Small shipments: minimums and flat rates

Below roughly 0.01 CBM, sea freight stops making sense — the handling outweighs the cargo. That is what air freight is for: 5–7 day lead time, billed per kilogram, minimum of 1 kg. Our sea service has no minimum CBM and flat rates for small packages, so the practical rule is: bulky and patient goes by sea, small and urgent goes by air. The full comparison is in sea vs air freight.

How to pay less for the same goods

Ask for export packing. Retail boxes inside shipping cartons waste space you pay for. Suppliers can often pack the same units 15–20% tighter if asked.

Consolidate. Three suppliers’ goods combined into one shipment at the forwarder's warehouse usually beats three separate small shipments, because partial cartons round up.

Watch the last carton. 7 full cartons plus one nearly-empty one bills the same as 8 full ones. Sometimes one SKU more or less changes the math.

Related reading

• How much does shipping from China cost?
• How to compute landed cost
• Sea freight vs air freight
• LCL vs FCL shipping