What is CBM in shipping?

CBM stands for cubic metre (m³), the standard unit of volume in international freight. It is calculated by multiplying a package's length, width and height in metres. Freight forwarders use CBM both to quote LCL (less than container load) rates and to work out chargeable weight, because light bulky cargo is billed by volume rather than by actual weight.

How do I calculate CBM for a carton?

Convert the carton dimensions to metres, then multiply length × width × height. A carton measuring 60 × 40 × 40 cm is 0.6 × 0.4 × 0.4 m, which equals 0.096 m³ per carton. Multiply by the number of cartons to get total CBM — for example 100 such cartons come to 9.6 m³.

How do I convert CBM to kilograms?

There is no fixed conversion — it depends on the cargo density. Air freight typically uses a volumetric factor of 1 m³ = 167 kg, while sea LCL often uses 1 m³ = 1,000 kg as the break-even. If the actual weight is higher than the volumetric weight, you are charged on actual weight; if lower, you are charged on volume.

How many CBM fit in a 20ft and 40ft container?

A 20GP holds 33.2 m³ nominally and loads to roughly 28–31 m³ in practice. A 40GP holds 67.7 m³ nominal, a 40HQ holds 76.3 m³, and a 45HQ holds 86.1 m³. Real loads typically reach 80–90% of those figures depending on how well the carton dimensions divide into the container's internal dimensions.

CBM Calculator — work out cubic metres for cartons, pallets and containers

CBM (cubic metre, m³) is the unit every freight quote is built on. This page explains how to calculate it by hand, when it decides your freight bill, and how to convert it to chargeable weight — with a free calculator for your own cartons.

The one-line formula: CBM = length (m) × width (m) × height (m) × quantity. That's it — the arithmetic is easy; the judgement (which measurement, when it matters, what buffer to add) is where people get the quote wrong.

1. What CBM means and why forwarders care

Shipping costs are driven by how much space your cargo takes up and how much it weighs. CBM is the space half of that equation. For full container loads (FCL) it tells you whether your goods will actually fit in the box you booked. For less-than-container loads (LCL) it is the unit your freight is priced in.

Most LCL rates are quoted per CBM or per "W/M" (weight or measure — whichever is greater). A forwarder will take your total volume, convert it to a volumetric weight, and compare it against the actual gross weight. The higher of the two is what you pay for.

Mode	Volumetric factor	Meaning
Sea LCL	1 CBM = 1,000 kg	1 m³ breaks even against 1 tonne
Air freight	1 CBM = 167 kg	1 m³ (or 6,000 cm³/kg) breaks even against 167 kg
Express / courier	1 CBM = 200 kg	Bulkier allowance than standard air
Road freight (LTL)	1 CBM = 333 kg	Varies a lot by carrier and lane

These factors are conventions, not physics. Every carrier sets its own. Always confirm the divisor your forwarder actually uses before you build a cost model on it — the difference between 1:167 and 1:200 on a 10 m³ shipment is real money.

2. How to calculate CBM step by step

Step 1 — measure in centimetres, convert to metres

Cartons are almost always measured in cm. Divide by 100 to get metres. A 60 × 40 × 40 cm carton is 0.6 × 0.4 × 0.4 m.

Step 2 — multiply to get single-unit CBM

0.6 × 0.4 × 0.4 = 0.096 m³ per carton.

Step 3 — multiply by quantity

100 cartons × 0.096 m³ = 9.6 m³.

Step 4 — compare against container capacity

A 20GP nominally holds 33.2 m³. On paper, 9.6 m³ is only 29% full. But that number is meaningless until you know whether the cartons actually divide into the container's internal dimensions — see section 4.

Worked example, mixed cartons. 200 cartons at 60 × 40 × 40 cm = 19.2 m³. 80 cartons at 80 × 60 × 50 cm = 19.2 m³. Total = 38.4 m³. That no longer fits a 20GP (33.2 m³ nominal) and will need a 40GP — a decision worth making before you book, not after.

3. Palletised cargo: the CBM you actually pay for

When goods are stacked on pallets, the billable volume is the pallet's footprint, not the cartons. A standard EUR pallet is 120 × 80 cm; a standard US pallet is 120 × 100 cm. Add the load height, including the 15 cm pallet itself.

Pallet type	Footprint	Loaded height	CBM per pallet
EUR / Euro	120 × 80 cm	160 cm	1.54 m³
EUR / Euro	120 × 80 cm	190 cm	1.82 m³
Standard US	120 × 100 cm	160 cm	1.92 m³
Standard US	120 × 100 cm	190 cm	2.28 m³

Notice how much bigger these numbers are than the equivalent loose cartons. A pallet of cartons that would measure 1.2 m³ loose occupies 1.5–1.8 m³ of billable space once stacked. Palletising typically costs you 30–50% of your container volume — which is why forwarders push loose loading whenever the cargo allows it.

4. CBM is not what fits — this is the mistake that costs money

Here is the trap. Divide container volume by carton volume and you get a number that looks authoritative. A 40HQ has 76.3 m³; cartons of 0.096 m³ divide into it 794 times. So "794 cartons fit"?

No. That calculation assumes cargo fills space like water. Real cartons are rigid rectangles, and whether they nest efficiently depends on how their dimensions divide into the container's internal length, width and height.

Container	Internal L × W × H (cm)	Nominal CBM	Realistic loaded CBM
20GP	589 × 235 × 239	33.2	28–31
40GP	1203 × 235 × 239	67.7	57–63
40HQ	1203 × 235 × 269	76.3	64–71
45HQ	1351 × 245 × 269	86.1	73–80

A carton that nests perfectly might reach 95% of nominal. One whose dimensions leave a 20 cm sliver along the container wall might only reach 75%. The gap between best and worst layout of the same cargo is routinely 15–25%.

⚠️ Practical rule: never promise a customer "container volume ÷ carton volume". Add a 5–10% buffer to the honest calculated figure, and verify the actual layout with a 3D loading tool before you commit to a delivery date.

5. When CBM is ruled by weight instead

CBM only decides your cost while the cargo is light. Once density climbs past the container's break-even point, weight becomes the binding constraint and no amount of clever loading helps.

Container	Payload limit	Break-even density	Cargo above this is weight-limited
20GP	21,700 kg	653 kg/m³	Dense cargo — you run out of weight first
40GP	26,500 kg	391 kg/m³	Most machinery, liquids, tiles
40HQ	26,500 kg	347 kg/m³	Most furniture, appliances
45HQ	27,000 kg	314 kg/m³	—

Read that table the other way and it becomes a planning tool: if your cargo density is below the break-even figure, you are volume-limited and should shop for the container with the most cubic metres per dollar. If it is above, you are weight-limited and the bigger container buys you nothing.

6. Frequently asked questions

What is CBM in shipping?: CBM stands for cubic metre (m³), the standard unit of volume in international freight, calculated as length × width × height in metres. Forwarders use it to quote LCL rates and to derive chargeable weight, because light bulky cargo is billed by the space it occupies rather than its actual weight.
How do I calculate CBM for a carton?: Convert dimensions to metres and multiply: a 60 × 40 × 40 cm carton is 0.6 × 0.4 × 0.4 = 0.096 m³. Multiply by quantity for the total — 100 cartons give 9.6 m³.
How do I convert CBM to kilograms?: There is no universal conversion; it depends on the cargo density and the carrier's factor. Air freight commonly uses 1 m³ = 167 kg and sea LCL uses 1 m³ = 1,000 kg. You are charged on whichever is greater, actual or volumetric weight.
How many CBM fit in a 20ft or 40ft container?: Nominal capacity is 33.2 m³ for a 20GP, 67.7 m³ for a 40GP, 76.3 m³ for a 40HQ and 86.1 m³ for a 45HQ. Realistic loads reach roughly 85–90% of those figures, depending on how the carton dimensions divide into the container.
Does palletising increase my CBM?: Yes, usually by 30–50%. The pallet footprint and the air gaps between pallets become billable volume, so the same cartons occupy noticeably more space on pallets than loose.
How do I check whether my own cargo actually fits?: Use the Container Loading Calculator: enter each carton's dimensions, quantity and weight, choose the container type, and it calculates how many units fit, the loading efficiency, the weight used, and draws a 3D loading plan. Free, no installation.

Enter your carton dimensions and get the real CBM, the loading efficiency and a 3D plan

Open the Container Loading Calculator →