Shipping Guides

How CBM Pricing Works for Sea Freight from China

Updated 2026 · 5 min read

If you’ve asked for a sea freight quote and been given a number per "CBM," this explains exactly what that means, how to calculate it yourself, and the packing habits that quietly inflate it.

Quick summary

CBM (cubic metre) = length × width × height of your cargo, in metres. Sea freight is priced per CBM regardless of weight, so a large light box costs as much to ship as a large heavy one. Measure the outer dimensions of the packed box, not the product itself, and minimise empty space to keep your CBM — and your quote — down.

What CBM Actually Measures

CBM stands for cubic metre. For sea freight, forwarders calculate CBM using the outer dimensions of your packed cargo — the box, crate, or pallet as it will actually travel, not the bare product inside it. The formula is simple:

The formula

CBM = Length (m) × Width (m) × Height (m)

If your measurements are in centimetres, divide each by 100 first. A box measuring 60cm × 50cm × 40cm becomes 0.6m × 0.5m × 0.4m = 0.12 CBM.

Worked Example

Box dimensions (cm)	In metres	CBM
60 × 50 × 40	0.6 × 0.5 × 0.4	0.12 m³
100 × 80 × 60	1.0 × 0.8 × 0.6	0.48 m³
120 × 100 × 100	1.2 × 1.0 × 1.0	1.20 m³

If you have several boxes in one shipment, calculate the CBM of each and add them together — that total is what your sea freight quote will be based on.

Why Weight Doesn’t Matter Here

This is the part that surprises first-time shippers: a box of lightweight inflatable toys and a box of the exact same dimensions full of dense hardware cost the same to ship by sea, because sea freight is priced by the space your cargo occupies in the container, not what it weighs. (Air freight works the opposite way — see our air vs sea comparison for when that matters.)

Three Ways CBM Quietly Grows

01

Oversized boxes

A product that would fit a smaller box, shipped in a larger one "for safety," inflates CBM for no real benefit. Right-sized packaging keeps volume down.
02

Excess internal padding

Bulky foam or air pillows protect goods but also take up billable space. A good warehouse team repacks to balance protection against wasted volume.
03

Irregular or non-stackable shapes

Awkward shapes that can’t pack tightly against other cargo effectively "waste" surrounding container space, which can be reflected in the quote.

This is exactly why consolidation and inspection at a China warehouse — repacking multiple orders together before the international leg — tends to produce a noticeably lower CBM than shipping each order in its original, oversized retail packaging.

LCL vs FCL: Does CBM Still Apply?

For LCL (less-than-container-load) shipments, yes — you’re charged per CBM because you’re sharing container space with other shipments. For FCL (full-container-load) , you pay a flat rate for the whole container regardless of exact CBM, which becomes cost-effective once your shipment’s volume approaches a standard container’s capacity. A forwarder can tell you the crossover point where FCL becomes cheaper than LCL for your specific cargo.

Frequently Asked Questions

Do I need to measure my own boxes, or does the forwarder do it?

Forwarders measure and weigh cargo at the warehouse before quoting, so you don’t need exact figures upfront — but knowing roughly how bulky your order is helps you sanity-check the quote and decide between air and sea.

Is there a minimum CBM for sea freight?

This varies by forwarder and route. Ask directly — some have a practical minimum charge for very small LCL shipments, in which case air freight may end up cheaper for tiny orders anyway.

Can repacking really lower my quote?

Yes. Since price is driven by volume, removing wasted space directly reduces CBM. This is one of the main reasons consolidating multiple orders at a warehouse before shipping is cheaper than shipping each one separately in its original packaging.

What if my cargo isn’t a neat box shape?

Irregular items are still measured by their maximum length, width, and height (the smallest box that would contain them), so oddly-shaped cargo can end up with a higher effective CBM than its actual volume.

Want an actual CBM quote for your cargo?

Send us your box dimensions or item list and we’ll calculate the CBM and quote sea freight directly.

Get a CBM Quote