Enter a box size and weight in either system. This converts both at once, inches to centimetres and millimetres and pounds to kilograms, with the volume in every common unit.
US carriers quote in inches and pounds. Suppliers and marketplaces abroad often use centimetres and kilograms. Convert once and copy the lot.
1 inch is exactly 2.54 centimetres and 1 pound is exactly 0.45359237 kilograms. Every other figure comes from those two.
| From | To | Multiply by |
|---|---|---|
| Inches | Centimetres | 2.54 |
| Centimetres | Inches | 0.3937 |
| Pounds | Kilograms | 0.4536 |
| Kilograms | Pounds | 2.2046 |
| Pounds | Ounces | 16 |
| Ounces | Grams | 28.35 |
| Cubic feet | Litres | 28.32 |
| Cubic metres | Cubic feet | 35.31 |
UPS rounds each dimension up to the next whole inch and any fraction of a pound up to the next pound. USPS began rounding every fractional dimension up to the next inch on 12 July 2026. So a box that converts to 11.02 in is billed as 12 in, and a 1.1 lb parcel is billed as 2 lb.
Once you have the size in inches, the dimensional weight calculator shows what a parcel will bill at and the cubic feet calculator gives the volume of a whole shipment.
2.54, exactly. The inch is defined that way.
About 2.2046. The pound is defined as exactly 0.45359237 kilograms.
Carriers round up to whole inches and whole pounds before they bill, so their number is often a little higher than the exact conversion.
Whichever your carrier bills in. For US parcels that is inches and pounds, so measure in those if you can and skip the rounding surprises.
Tell us your orders a month and units per order. You see a per-order price before you commit to anything.
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