How to calculate container CBM, step by step

Updated: 13 November 2026

Working out the CBM of a shipment is the first calculation of any container booking: how many cubic metres it takes up and which equipment it fits in. The maths is simple, but there are two traps: a container is never filled completely and, quite often, weight runs out before volume does.

What is container CBM?

CBM stands for cubic metre: the volume a shipment takes up, worked out to know how much space it needs and which container it fits in. In the trade you will hear it as “the CBM of the packing list” or simply “the cube”.

CBM answers a question about space. Whether the cargo can actually travel that way (weight, distribution, securing) is a different question, covered further down. If you want to know what a 3D tool does, we explain it in 3D container load calculator: what it does and doesn’t do.

How do you calculate the cubic metres of a shipment?

Package by package, with the packing list in front of you:

1. Measure each package on the outside, with its packaging and, if it is palletised, with the pallet. Take the outermost point, not the product size.
2. Convert the dimensions to metres. 60 cm is 0.60 m.
3. Multiply length × width × height. That is the volume of one package: 0.60 × 0.40 × 0.50 = 0.12 m³.
4. Multiply by the number of units on that line.
5. Add up all the lines. That is the CBM of the shipment.

If you work in centimetres, divide the result by 1,000,000 to go from cm³ to m³. If your supplier gives you cubic feet, 1 m³ is about 35.3 cubic feet. To skip the manual maths, use the CBM calculator, and to collect each package’s details, the packing list template.

How many m³ does each container hold?

These are the interior volumes and typical payloads of the most common dry containers:

Container	Interior approx. (L × W × H)	Volume	Payload approx.
20′ Dry Van	5.90 × 2.35 × 2.39 m	33 m³	28,100–30,200 kg
40′ Dry Van	12.03 × 2.35 × 2.39 m	67–68 m³	26,500–28,800 kg
40′ High Cube	12.03 × 2.35 × 2.69–2.70 m	76 m³	26,300–28,800 kg

Source: shipping lines’ equipment specifications (Hapag-Lloyd, ONE, Maersk). Interior dimensions vary slightly by manufacturer, and the exact payload of each unit comes from its CSC plate. The other container types are covered in shipping container types.

Why is a container never 100% full?

Because cargo is not a liquid. Between the interior volume and what actually fits there are several losses:

• Gaps. Package sizes rarely divide the interior length, width and height exactly: there are always strips where nothing fits.
• Stacking. Nothing goes on top of a package that cannot bear weight, so all the space up to the roof is lost.
• Orientation. Packages that must stay upright or cannot be rotated fit less well.
• The door. Everything has to go through it: about 2.34 × 2.28 m on a standard 20′ or 40′.
• Securing. Chocks, dunnage and air bags take up space too, and the CTU Code requires cargo that cannot shift.

An example with pallets: 24 EUR pallets of 1.20 × 0.80 m, 1.50 m high and not stackable, fill the floor of a 40′. Their volume is 24 × 1.20 × 0.80 × 1.50 = 34.56 m³: the container is full with half of its 67–68 m³ used. How many pallets fit in each container is explained in how many pallets fit in a container.

When does weight limit and when does volume?

Your cargo’s density tells you: its total weight in kilos divided by its cubic metres. Compare it with the container’s, which is its payload divided by its volume:

Container	Payload ÷ interior volume
20′	about 850–915 kg per m³
40′	about 390–430 kg per m³
40′ HC	about 345–380 kg per m³

Calculated with the figures in the table above and the full interior volume. Since a container is never filled completely, the real point where weight and volume meet is somewhat higher.

• If your cargo is less dense, space runs out first: look for more volume (a 40′ or a 40′ HC).
• If it is denser, payload runs out first: a bigger container will not let you load more, and a 20′ is usually enough.

The weight includes the packaging, pallets and securing material. And the packed container needs its VGM before it is loaded on board.

A step-by-step CBM example

A general cargo packing list with two lines:

Line	Dimensions (L × W × H)	Units	m³ per package	Total m³	Total weight
Cardboard boxes	60 × 40 × 50 cm	120	0.12	14.40	2,160 kg (18 kg/box)
EUR pallets, not stackable	120 × 80 × 150 cm	10	1.44	14.40	4,500 kg (450 kg/pallet)
Total				28.80 m³	6,660 kg

1. Volume. 28.80 m³. At first sight, it fits in a 20′, which holds about 33 m³.
2. Density. 6,660 kg ÷ 28.80 m³ ≈ 231 kg per m³. Far below the 20′ figure: volume is the limit and the weight stays well under the payload.
3. Placement. This is where the total falls short. The 10 pallets take 10 of the 11 EUR pallet positions on the floor of a 20′ and cannot be stacked. Above each one there are about 0.89 m left (2.39 − 1.50): a single layer of boxes, and only if the pallet can bear weight. On the free floor there is room for 6 boxes per layer in 4 layers (24), and on top of the pallets, 4 per pallet (40): about 64 of the 120.
4. Result. The CBM total says 20′; the placement says 40′. In a 40′, the 10 pallets use 10 of its 23–25 positions, and the 120 boxes, if they can be stacked four high (2.00 m), take about 8 more. It fits, with room to secure the cargo, and the weight stays well under the payload.

This is the most expensive CBM mistake: booking the equipment on the cubic metres and finding out at the dock that the cargo does not fit.

What are the most common CBM mistakes?

• Measuring the product, not the package. Packaging and pallets take up space too.
• Mixing centimetres and metres. 60 × 40 × 50 is 120,000 cm³, that is 0.12 m³, not 120.
• Using the container’s external dimensions. On the outside a 20′ measures 6.06 × 2.44 × 2.59 m, but you load the inside.
• Assuming the container fills up completely. Gaps, stacking and securing take part of the volume.
• Forgetting the weight. Cargo that fits can still exceed the container’s payload.
• Rounding down. One centimetre per package, times a hundred packages, is a row that does not fit.

When is the CBM total not enough?

When placement matters as much as volume, which is almost always unless the cargo is identical boxes:

• Some packages cannot be stacked, are fragile or must stay upright.
• There are tall pallets that leave space you cannot use.
• The packing list mixes very different sizes.
• The cargo is heavy and has to be spread along and across the floor, as the CTU Code requires.
• A package is close to the size of the door.
• The shipment needs more than one container.

That is when you need a load plan: where each package goes and in what order. And, before booking, a check that the plan can travel that way: payload, VGM and weight distribution. That is the difference between calculating and validating, explained in load validation vs load calculation. To choose the equipment from your pallets, m³ and weight, see which container do I need.

With the container validator you enter the packing list, choose the equipment and see whether the cargo fits and can travel that way: a verdict, each warning with its reason, and the load plan, which you can share as a link or as a PDF load manifest. To try it with your own cargo, validate it. The validation uses the data you enter: it does not replace the weighbridge.

Validate this type of load: Validate a container load.

Sources

• Hapag-Lloyd: Container Specification (includes the ISO 668 table of external dimensions)
• ONE: Container Information (dry, reefer, open top and flat rack)
• Maersk: equipment specifications (dry)
• ISO 668: dimensions of series 1 containers
• EN 13698-1: EUR pallet, 1,200 × 800 mm
• MSC.1/Circ.1497: full text of the CTU Code
• IMO: Verification of the gross mass of a packed container (SOLAS, chapter VI, regulation 2)
• NIST: Guide to the SI, Appendix B.9 (cubic foot to cubic metre)

Validate your load before it ships.