What volumetric weight means
Couriers and airlines run out of space before they run out of weight. A big box of pillows takes the room of a heavy box but weighs very little, so carriers charge by whichever is larger: the real weight on the scale, or a volumetric (dimensional) weight worked out from the box size.
The formula
Volumetric weight (kg) = Length × Width × Height (cm) ÷ divisor
Chargeable weight = the higher of actual weight and volumetric weight, rounded up to the courier’s slab
The divisor is set by the carrier. 5000 is the most common for air and express (it means 5,000 cm³ is treated as 1 kg). A smaller divisor, such as 4000, makes the volumetric weight higher. Check your courier’s rate card or contract — it is always printed there.
Worked example
A 40 × 30 × 20 cm carton weighing 3.2 kg: 40 × 30 × 20 = 24,000 cm³. Divided by 5000 = 4.8 kg volumetric. The courier charges for 4.8 kg, which rounds up to 5 kg on a 0.5 kg slab — even though the parcel weighs 3.2 kg.
How to pay for less
- Use the smallest box that protects the item. Cutting 5 cm off each side of the example box drops it to 2.6 kg volumetric — now the actual 3.2 kg is charged instead.
- Measure the outside of the box, at the widest point, including bulges. Couriers re-measure at the hub and bill the difference.
- Combine small items into one carton rather than several half-empty ones, since each box is rounded up separately.
- Surface vs air: for heavy, dense shipments that are not urgent, surface (road) services often charge per CFT or per kg at a lower rate.
CFT for surface cargo
For road freight in India, bulky consignments are often billed by cubic feet (CFT): 1 CFT = 28,316.8 cm³. If a carrier charges “6 kg per CFT”, a 2 CFT carton is billed at no less than 12 kg. Enter the carrier’s CFT factor above to see it.
Questions people ask
Is volumetric weight the same for every courier?
Do I use inches or centimetres?
Why was I charged more than the calculator shows?
Does volumetric weight apply to documents?
Sources
- IATA dimensional weight convention (6000 cm³/kg for air cargo)
- Your courier’s published rate card and terms of carriage
Results are estimates to help you plan. Always confirm important numbers with the seller, carrier or authority concerned. Last reviewed: November 2026.