The formula
Volumetric weight (kg) = L × W × H (cm) ÷ divisor
In inches and pounds: L × W × H (in³) ÷ divisor = lb, where common divisors are 139 or 166 in³ per pound.
Worked examples
- Express parcel. 50 × 40 × 30 cm, 6 kg actual, divisor 5000: 60,000 ÷ 5000 = 12 kg. Chargeable weight: 12 kg.
- Dense carton. 30 × 20 × 20 cm, 15 kg actual, divisor 5000: 12,000 ÷ 5000 = 2.4 kg. Chargeable weight: 15 kg (actual is higher).
- Multiple pieces. 10 cartons of 40 × 30 × 25 cm, divisor 6000: 30,000 ÷ 6000 = 5 kg each, 50 kg in total, compared with the total actual weight.
Step by step
- Measure the outside of the packed carton at its longest points, in the same unit.
- Multiply length × width × height.
- Divide by the divisor stated in your carrier's rate card.
- Compare with the actual weight; the larger one is the chargeable weight.
- Apply the carrier's rounding (some use 0.5 kg steps).
Common mistakes
- Using the product size instead of the outside carton size.
- Mixing centimetres and inches.
- Forgetting that each carton is rated separately when a shipment has several.
Skip the arithmetic with the volumetric weight calculator.