How to Calculate CBM for Shipping (Formula, Examples & Chargeable Weight)

Quick answer: CBM (cubic metres) is just length × width × height, with all three in metres. A carton measuring 0.40 × 0.30 × 0.25 m is 0.03 CBM; 100 of them is 3 CBM. Carriers use your total CBM, alongside actual weight, to price freight and decide how much container space you need.

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The CBM formula

CBM = length (m) × width (m) × height (m)

For a whole shipment, work out the CBM of one carton, multiply by the quantity, and add up every carton type:

Total CBM = Σ (carton CBM × quantity)

Worked example

A shipment of 120 cartons, each 50 × 40 × 30 cm:

1. Convert to metres: 0.50 × 0.40 × 0.30 m
2. Volume of one carton: 0.50 × 0.40 × 0.30 = 0.06 CBM
3. Total: 0.06 × 120 = 7.2 CBM

That’s it. If your cartons come in several sizes, repeat steps 1–2 for each and sum the totals.

Converting from centimetres or inches

Measuring in something other than metres? Divide at the end:

Measured in	Formula	Example
Centimetres	(L × W × H) ÷ 1,000,000	50 × 40 × 30 = 60,000 ÷ 1,000,000 = 0.06 CBM
Millimetres	(L × W × H) ÷ 1,000,000,000	500 × 400 × 300 = 0.06 CBM
Inches	(L × W × H) ÷ 61,024	20 × 16 × 12 = 3,840 ÷ 61,024 = 0.063 CBM

And to switch between metric and imperial volume: 1 CBM ≈ 35.315 cubic feet (CFT).

CBM → chargeable weight (what you actually pay)

Carriers bill the greater of your actual weight and your volumetric (dimensional) weight, so light, bulky cargo is priced on volume:

• Sea LCL: the rule of thumb is 1 CBM = 1,000 kg. If your shipment is 7.2 CBM and weighs 4,000 kg, you’re billed on the 7,200 kg volumetric figure.
• Air freight: volumetric weight = (L × W × H in cm) ÷ 6,000 per piece. A 100 × 60 × 50 cm box = 300,000 ÷ 6,000 = 50 kg volumetric, even if it weighs 30 kg on the scale.

Knowing which one binds — weight or volume — tells you whether to focus on lighter packaging or tighter stacking.

CBM and container choice

Once you know your total CBM, compare it to a container’s usable volume (full dimensions here):

Container	Usable volume	Realistic CBM loaded (~80%)
20ft	~33.2 m³	~25–28 CBM
40ft	~67.7 m³	~54–58 CBM
40ft High Cube	~76.4 m³	~60–65 CBM

As a tipping point, shipments under ~15 CBM usually go LCL (you share a container and pay per CBM); above that, a full FCL 20ft is often cheaper. You’ll never load a container to 100% of its rated volume — boxes don’t tile perfectly and weight limits bite — so plan around ~80%.

Skip the spreadsheet

Adding up cartons by hand is error-prone the moment sizes vary. The free CBM calculator totals a mixed carton list instantly and shows utilisation across 20ft and 40ft containers. And when you’re ready to see exactly how the cargo loads, ContainerMath — full container loading software — turns the same list into a 3D load plan with live volume and weight.

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Frequently asked questions

What is CBM in shipping?

CBM stands for cubic metre — the total volume of your cargo (length × width × height). Carriers use it, alongside actual weight, to price freight and allocate container space.

How do I calculate CBM for multiple cartons?

Work out the CBM of one carton (L × W × H in metres), multiply by the quantity, and add up each carton type. For example, 100 cartons of 0.03 CBM = 3 CBM total.

How do I convert CBM to kg?

For sea LCL the standard conversion is 1 CBM = 1,000 kg of volumetric weight. You’re charged on whichever is higher — actual or volumetric weight.

How many CBM are in a 40ft container?

A 40ft container has about 67.7 m³ of internal volume, but you’ll realistically load ~54–58 CBM once you account for packing gaps and the weight limit.