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CBM Calculator

CBM stands for cubic metre, and it is the unit shipping runs on. Nearly every sea freight price, every warehouse rate and every quotation for a shared container starts with this one number, and it is the first thing a forwarder will ask you for.

Working it out is simple arithmetic, but the mistakes are easy to make: measuring the product instead of the packed box, forgetting the pallet, or mixing up centimetres and metres by a factor of a million. Put your boxes in below and the number comes out, along with what it actually means for your shipment.

Your boxes

One line for each size. Measure the outside of the packed box: the carton, the shrink wrap, and the pallet if it is going on one. That is what the carrier measures.

What that volume means

How much fits in a container

The space inside a container, for planning. Real loading never reaches these numbers, because boxes do not tessellate perfectly and you need room to work.

Container	Inside space	Weight you can load	Worth knowing
20ft standard	33.2 m³	28,250 kg	The workhorse. Heavy cargo fills the weight limit long before it fills the space.
40ft standard	67.7 m³	26,700 kg	Twice the space of a 20ft but slightly LESS weight allowance. This surprises people every week.
40ft high cube	76.4 m³	26,580 kg	One foot taller inside. The usual choice for light bulky cargo, and normally only a little more than a 40ft.
45ft high cube	86.1 m³	27,700 kg	Not available everywhere, and some road authorities restrict it. Check before you plan around one.

Look at the second and third columns together on the 20ft and the 40ft. The 40ft has twice the space and slightly less weight allowance. If your cargo is dense, two 20ft containers may carry more than one 40ft, and that catches people out constantly.

Tap a heading to read it.

How to work it out by hand

Multiply length by width by height, in metres. That is it.

If your measurements are in centimetres, which they usually are, multiply the three numbers together and then divide by 1,000,000. A box 120 by 80 by 100 centimetres is 960,000 cubic centimetres, which is 0.96 cubic metres.

The million is where people go wrong. There are 100 centimetres in a metre, but 100 times 100 times 100 cubic centimetres in a cubic metre. If your answer looks a thousand times too big or too small, that is the reason.

Then multiply by how many boxes. Twenty of those boxes is 19.2 cubic metres.

What the number is used for

Shared container freight is usually priced per cubic metre, or on the greater of the volume and the weight. Warehouse storage is often priced per cubic metre per week. And the volume is what decides whether your cargo fits in one container or needs two, which is a much bigger cost step than any rate negotiation.

The four measuring mistakes

Measuring the product, not the packing. A television is not the size of the box a television ships in. The carrier measures the box.

Forgetting the pallet. A standard pallet adds about 15 centimetres of height and often a little length and width. On a stack of pallets that is real money.

Measuring the middle of a bulging carton. Overpacked cartons bulge, and the carrier measures the widest point. If your boxes are full to bursting, measure them full.

Rounding down. Carriers round up, usually to the nearest whole or half unit. Rounding down at your end means your quotation is lower than the invoice, and the difference comes out of your margin.

One habit

Take the measurements yourself, or ask the supplier for them in writing before you agree a price. "About a pallet and a half" is not a measurement, and every freight dispute over volume starts with somebody guessing.

Container figures are the common industry standards. Real containers vary a little by owner, age and build, and the weight you are allowed to load also depends on the road limits at both ends. Confirm with your carrier before planning to the last kilo.

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