CBM describes volume in cubic metres. Gross weight measures physical mass, including packing. Volumetric weight converts occupied space into a weight equivalent using a service-specific divisor. These numbers are related, but they are not interchangeable.

Start with packed measurements

Ask for external packed dimensions, not the dimensions of the product before packing. Record length, width and height with their units, plus the gross weight and number of identical pieces. Group different package sizes separately.

A simple measurement sheet is more useful than a single unsupported “total volume” figure. It lets the forwarder check the arithmetic and see whether one unusually large piece needs attention. Use our shipment worksheet to record the dimensions and assumptions.

Calculate CBM step by step

CBM = length (m) × width (m) × height (m) × identical pieces

Using centimetres: CBM = L × W × H × pieces ÷ 1,000,000

Worked example: four crates, each 120 × 100 × 100 cm, occupy 1.2 × 1 × 1 × 4 = 4.8 CBM. If each weighs 200 kg gross, the total gross weight is 800 kg. Volume and weight must both appear in the cargo brief.

For mixed sizes, calculate each group and add the volumes. Two cartons at 60 × 40 × 50 cm total 0.24 CBM. One crate at 100 × 80 × 75 cm adds 0.60 CBM. Together they total 0.84 CBM. Do not multiply every package by the dimensions of the largest one unless that is genuinely how they are packed.

Apply the quoted airfreight divisor

DHL Global Forwarding illustrates air volumetric weight using centimetres divided by 6,000 and compares it with gross weight. It also warns that carrier density ratios can differ. Read its chargeable-weight explanation.

Illustrative volumetric kg = L(cm) × W(cm) × H(cm) × pieces ÷ 6,000

For the four crates above, the calculation is 4,800,000 ÷ 6,000 = 800 volumetric kg. Against 800 kg gross, both values are equal before any applicable rounding or minimum-charge rule.

If the same packed volume instead weighed 500 kg gross, the illustrated volumetric amount would still be 800 kg. If it weighed 950 kg gross, the physical weight would be higher. This example shows why both measurements matter; it is not a freight quotation.

Do not transfer a divisor between services

DHL Express’s UK guidance uses a divisor of 5,000 and describes calculating multiple packages separately. That is different from the Global Forwarding example. Read the Express guidance.

For the same 4,800,000 cubic centimetres, dividing by 5,000 gives 960 volumetric kg. The arithmetic is correct in both examples; the applicable service rule determines which calculation is relevant. Ask for the divisor, package-versus-shipment assessment, rounding and minimum charge in the actual offer.

Turn the numbers into a better enquiry

Send the measurements rather than only your calculated result. Ask the provider to confirm the charging basis and any packing or handling constraints. Use this checklist before comparing prices:

Check	Why to clarify it
Units on every measurement	A figure labelled only “120” is ambiguous.
Packed gross weight	Product net weight leaves out the packing.
Mixed-size groups	One average carton size can hide an exceptional piece.
Stacking and handling	A geometric volume does not describe every physical handling constraint.
Rounding and minimums	A calculated weight is not automatically the final billed quantity.
Other charges	Multiplying kilograms by a rate does not establish the full shipment cost.

Do not apply an airfreight divisor to an LCL sea quotation. Ask which volume/weight basis, minimums and local charges apply to that specific ocean offer. Compare the full scope using our quotation comparison guide.

Does a lower CBM always mean a lower invoice?

No conclusion can be drawn from volume alone. First compare the applicable charging quantity, service scope and quoted terms. Avoid reducing protective packing solely to lower a calculation without checking cargo protection and acceptance requirements.

For a shipment-specific discussion, explore air freight or sea freight and provide the final packed measurements.

Sources & editorial note

Sources checked 18 October 2026. Carrier guidance supports the stated concepts; it is not a Catalyst tariff, endorsement or service guarantee. Examples and checklists are original editorial aids. Prepared for Catalyst Shipping. For shipment-specific requirements, consult the commercial team before booking.

CBM and air chargeable weight explained