How volumetric weight is calculated
Multiply the length, width and height of the box in centimetres and divide by the divisor. With inches, the same formula applies after converting to centimetres, which this tool does for you. The divisor is the number of cubic centimetres a carrier treats as one kilogram: the lower it is, the higher the volumetric weight.
- 50 × 40 × 30 cm ÷ 5000 = 12 kg
- 50 × 40 × 30 cm ÷ 6000 = 10 kg
- 60 × 60 × 60 cm ÷ 5000 = 43.2 kg
- A 12 kg box that weighs only 5 kg is charged as 12 kg
Which divisor to use
Express parcel services commonly use 5000. Air cargo generally uses 6000, the standard set by the airline association IATA, which equals 167 kg per cubic metre. Some road, economy and postal services use other figures, and a few ignore volume below a certain size. The divisor and rounding rules are part of each carrier's terms, so check the rate card or the booking page of the service you use before you rely on a quote.
Chargeable weight and rounding
You are billed on the chargeable weight, the higher of the actual and volumetric weight. Many couriers then round up, often to the next 0.5 kg for parcels, which the tool shows for kilograms. For several boxes on one shipment, carriers usually add up the boxes first, so the tool totals them for you. Sea freight is normally priced by volume in cubic metres instead, which is why the volume is shown too.
How to lower the cost
Volumetric weight punishes empty space. Use the smallest box that protects the item, cut down a box that is too tall, and avoid oversized padding. Soft items such as clothes can go in a padded bag rather than a carton. When you sell online, keep a few box sizes that fit your common orders: a few centimetres on each side can change the charge by several kilograms.