How to Calculate CBM for Shipping: Formula, Examples and Container Sizes

To calculate CBM (cubic meters), multiply a carton's length, width and height in meters, then multiply by the number of cartons. In centimeters, multiply the three sides and divide by 1,000,000: a 50 × 40 × 30 cm carton is 0.06 CBM, so 100 cartons are 6 CBM. In inches, divide cubic inches by 61,024.

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Freight forwarders quote sea freight by CBM, so it's the first number they ask for. Our free CBM calculator adds up several carton sizes at once and shows total CBM, cubic feet, gross weight, rough container fill and air-freight volumetric weight, all in your browser. This guide shows the formulas, worked examples, how much fits in a container, and how CBM turns into a price.

What is CBM in shipping?

CBM stands for cubic meter: the volume of a box 1 m long, 1 m wide and 1 m high. Shipping lines, freight forwarders and warehouses use it to measure how much space your goods take up. When you ship less than a full container (LCL), you pay for the space your cartons use, so the CBM figure largely sets your freight bill.

How do I calculate CBM?

Worked example with two carton sizes

1. 100 cartons of 50 × 40 × 30 cm: 0.06 CBM each, so 6.0 CBM.
2. 50 cartons of 60 × 40 × 40 cm: 0.096 CBM each, so 4.8 CBM.
3. Total: 6.0 + 4.8 = 10.8 CBM, or about 381 cubic feet.

Work out each carton size separately and add them up. Rounding each carton to two decimals before multiplying by hundreds of cartons can throw the total off, so keep the full figure until the end.

How many CBM fit in a shipping container?

Less than the container's internal volume. Cartons don't tessellate perfectly, pallets take space, and you need room to load. Use the internal volume as a ceiling and a lower usable figure for planning.

Internal volumes come from carriers' published container specifications and vary slightly by container. Weight can limit you before volume does with heavy goods, so check the payload limit too. Our calculator starts with usable volumes of 28, 58 and 68 CBM and lets you change them; your forwarder should confirm the real load plan before you book.

How is sea freight charged by CBM?

For LCL, forwarders charge per revenue ton, the higher of your volume in CBM and your weight in metric tons (1,000 kg). This is called the weight or measure (W/M) rule.

Most consumer goods ship by volume, which is why trimming carton size pays. Expect a minimum charge, often 1 CBM, plus origin and destination fees that don't scale with volume.

How is air freight charged?

On chargeable weight: the higher of actual weight and volumetric weight. A common air-cargo divisor is 6,000 cm³ per kg, and many express couriers use 5,000, which makes the same box bill heavier. A 50 × 40 × 30 cm carton weighing 8 kg has a volumetric weight of 60,000 ÷ 6,000 = 10 kg, so you pay for 10 kg. With a 5,000 divisor it bills at 12 kg.

A quick conversion: 1 CBM at a 6,000 divisor is about 167 kg of volumetric weight. For parcel shipments within a country, our dimensional weight calculator has carrier presets in inches and pounds or centimeters and kilograms.

How do I reduce my CBM?

• Right-size the master carton so there's little empty space around the inner boxes.
• Ask about flat-pack or nested packing for items that stack inside each other.
• Cut retail-packaging bulk; a slimmer gift box multiplies across thousands of units.
• Check carton height against the container so layers stack without wasted headroom.
• Consolidate orders from nearby suppliers into one shipment to spread fixed fees.

Then put the landed cost per unit (product, freight, duty, fees) into our profit margin calculator, and use the transit time in your reorder point so the next shipment leaves on time.

Measuring cartons correctly

1. Measure a packed, sealed carton, not the empty one or the product.
2. Take the outside length, width and height at the widest points, including any bulge.
3. Round up to the next whole centimeter or half inch.
4. Weigh a full carton for gross weight, and record it per carton size.
5. Ask your supplier for the packing list with carton dimensions and weights, and spot-check a few.

CBM quick reference

"Cartons per 1 CBM" is volume only; real stacking fits fewer. Use it to sanity-check a quote, not as a load plan.

Frequently asked questions

How do you calculate CBM for a carton?

Multiply length × width × height in meters. In centimeters, multiply them and divide by 1,000,000. A 50 × 40 × 30 cm carton is 60,000 ÷ 1,000,000 = 0.06 CBM.

How do you calculate CBM in inches?

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

How many cubic feet are in 1 CBM?

About 35.31 cubic feet. To convert cubic feet to CBM, divide by 35.31.

How many CBM is a 20 ft container?

About 33 CBM of internal volume, with roughly 25 to 28 CBM usable for cartons in practice. A 40 ft is about 67 CBM and a 40 ft high cube about 76 CBM.

Is 1 CBM equal to 1,000 kg?

Not physically, but for LCL sea freight pricing, 1 CBM is treated as equal to 1 metric ton. You're charged on whichever is higher, volume or weight.