How to calculate CBM for shipping
Measure finished cartons, convert units correctly, and calculate a mixed shipment's cubic meters without confusing volume with freight price.
Have your measurements ready? Put the method to work.
CBM CalculatorStart with the finished shipping package
CBM means cubic meters. For a rectangular carton, it describes the space enclosed by its length, width, and height. Measure the outside of the closed package, including protrusions or bulges, rather than the product inside it. A carton advertised by internal dimensions is not yet a shipping measurement.
Write each measurement and its unit together. For mixed cartons, create a separate line for each size and record how many cartons use that size. This prevents one small change in carton height from being applied incorrectly to the whole shipment.
Convert lengths before multiplying
Volume in cubic meters equals length in meters × width in meters × height in meters. From centimeters, divide the product of the three measurements by 1,000,000. From millimeters, divide by 1,000,000,000. Dividing by only 100 or 1,000 is a common error because all three axes need conversion.
An inch is exactly 0.0254 m and an international foot is exactly 0.3048 m. Therefore one cubic foot is 0.028316846592 m³. Use the exact factor internally and round only the displayed result.
Worked example: two carton sizes
Ten cartons measure 50 × 40 × 30 cm. One carton is 60,000 cm³, or 0.06 m³; that row totals 0.60 m³. Four more cartons measure 60 × 40 × 40 cm. Each is 0.096 m³, so the second row totals 0.384 m³.
The shipment volume is 0.60 + 0.384 = 0.984 m³, approximately 34.75 ft³. The shipment contains fourteen cartons. Keeping both row totals makes the result easier to reconcile against a packing list.
Carton volume and occupied space differ
Adding carton volumes does not prove that the cartons fit into a particular container. Gaps, differing shapes, pallet overhang, access space, and required restraints can consume additional room. If the goods travel on pallets, measure the complete loaded unit when that is the carrier's required basis.
Use the container loading calculator to examine feasible arrangements and the dimensional weight calculator to compare volume-based and scale weight. Neither calculation supplies a freight rate, minimum charge, surcharge, or carrier booking confirmation.
Keep a useful shipment record
Save the size, unit, quantity, and volume for each row. If you export a CSV, include the date and shipment reference in your own records. Recheck measurements after any packaging change; a few centimeters repeated across many cartons can materially change the total.
When a carrier rounds dimensions or applies a minimum billable volume, preserve the measured volume and document that separate billing adjustment. This makes a discrepancy explainable instead of silently altering the physical measurements.
Technical references
Service rules and equipment can change. Verify the specifications for your shipment.