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.

Worked example: a pallet

A palletised load is measured as it ships, so the pallet base counts. A Euro pallet (1.20 × 0.80 m) loaded to 1.60 m high, the 144 mm pallet included:

1. Volume: 1.20 × 0.80 × 1.60 = 1.536 CBM
2. Ten such pallets: 1.536 × 10 = 15.36 CBM

Measure the height from the floor to the highest point of the load, not the top of the cartons on one corner. If the cartons overhang the pallet edge, use the overhang, not the pallet footprint.

Worked example: a mixed shipment

Real shipments are rarely one carton size. Work each line out separately, then total both volume and weight:

Line	Size (cm)	Qty	CBM each	Total CBM	Total weight
Carton A	60 × 40 × 40	200	0.096	19.20	3,600 kg
Carton B	45 × 35 × 30	80	0.047	3.78	960 kg
Pallet C	120 × 100 × 150	4	1.800	7.20	2,600 kg
Total				30.18	7,160 kg

Keep the unrounded figure per carton (0.04725 for carton B) and round only the total. Rounding each carton to 0.05 would add over 0.2 CBM here, and on thousands of small cartons the error grows into a pallet’s worth of space.

Two things this table tells you straight away. The shipment is volume-heavy (30.18 CBM against 7.16 t), so it will be billed on volume. And 30.18 CBM is more than a 20ft will realistically hold, even though a 20ft’s internal volume is 33.2 m³. More on that below.

Round and irregular items: use the box they occupy

A drum, a roll or a pipe takes up the space of the rectangle around it, so carriers measure that rectangle. A standard 200-litre drum is about 58.5 cm across and 88 cm tall:

• Bounding box: 0.585 × 0.585 × 0.88 = 0.301 CBM
• The cylinder’s own volume is only about 0.236 m³, but nothing else can use the corners, so 0.301 is the number to quote.

Pipe works the same way for billing, but in a container you can nest each layer into the hollows of the one below, so more lengths fit than square boxes would suggest. How many pipes fit in a container has the counts by diameter.

The same rule covers machinery, furniture and anything with a bulge: measure the outermost point in each direction.

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), so divide cubic feet by 35.315 to get CBM. A carton of 2 × 1.5 × 1 ft is 3 ft³, or 3 ÷ 35.315 = 0.085 CBM.

Whatever unit you measure in, convert once, at the end. Converting each dimension to metres and rounding as you go (20 in ≈ 0.51 m) loses accuracy on every carton.

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.

On LCL quotes this appears as W/M (“weight or measure”), or as freight tons or revenue tons. One W/M is 1 CBM or 1,000 kg, whichever gives the higher count. The mixed shipment above is 30.18 W/M: its volume (30.18) beats its weight in tonnes (7.16). Most LCL tariffs also charge a minimum of 1 W/M, so a 0.4 CBM consignment still pays for a full cubic metre.

Air and courier freight use different divisors (6,000 for most air freight, 5,000 for most couriers), so the same box can cost very different amounts by mode. The dimensional weight guide compares them side by side.

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. Our guide to LCL vs FCL works through where the break-even falls. 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%.

That is why the 30.18 CBM mixed shipment above doesn’t go in a 20ft. On paper it is 91% of the box. In practice, carton A’s 60 × 40 cm footprint, carton B’s different height and four pallets that can’t be stacked leave gaps no division can see. Volume tells you the minimum space you need. Only a load plan tells you whether it actually fits.

Weight caps the other end. A 20ft’s payload is around 28 t, so cargo denser than about 850 kg per CBM fills the payload before the space. Above that density, plan by weight limits, not CBM.

Common CBM mistakes

• Measuring the product, not the package. CBM is measured on the outer carton or the loaded pallet, including the pallet base and any bulge.
• Rounding each carton. Round only the total. Per-carton rounding inflates (or shrinks) big shipments by whole pallets.
• Forgetting the pallets. A Euro pallet’s 144 mm base adds about 0.14 CBM before any cargo goes on it.
• Dividing container volume by carton volume. That gives a ceiling you will never reach. The real count comes from how the cartons tile; see how many boxes fit in a container.
• Assuming the carrier will agree. Forwarders and CFS warehouses remeasure. If their figure is higher, that’s the one on the invoice, so measure at the widest point.

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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.

How many CBM are in a 20ft container?

A 20ft container has about 33.2 m³ of internal volume. Plan on loading ~25–28 CBM of cartons, less if the load has pallets that can’t be stacked or a mix of carton heights.

How do I calculate CBM in inches?

Multiply length × width × height in inches and divide by 61,024. A 20 × 16 × 12 in carton is 3,840 cubic inches, or 3,840 ÷ 61,024 = 0.063 CBM.

What does W/M mean on a freight quote?

W/M means “weight or measure”. One W/M is either 1 CBM or 1,000 kg, whichever gives the higher number, and LCL freight is priced per W/M. Most tariffs charge a minimum of 1 W/M per shipment.

How do I calculate CBM for a pallet?

Measure the loaded pallet as it ships: the pallet’s length and width (or the cargo’s, if it overhangs) and the total height from the floor, pallet base included. A Euro pallet loaded to 1.6 m is 1.2 × 0.8 × 1.6 = 1.536 CBM.