Hong Life CalculatorsUnderstanding the volumetric weight calculator — concept and principle
Air freight and courier prices are not based on weight alone. A large, light box takes up space that could have carried heavy cargo, so carriers compare the actual weight with a "volumetric" (dimensional) weight worked out from the box size, and charge whichever is higher. This calculator gives you the volumetric weight, the chargeable weight and the box volume, so you can estimate a shipping bill or decide whether a smaller box is worth it.
How it is calculated
- Volumetric weight (kg) = length × width × height (cm) ÷ divisor
- Chargeable weight = the higher of actual and volumetric weight, rounded up to the next 0.5 kg
- Volume (m³) = L × W × H ÷ 1,000,000; volume (L) = L × W × H ÷ 1,000
The divisor is selectable. 6,000 is the IATA convention for air cargo; many express couriers use 5,000, which makes the same box "heavier".
The principle
The divisor is really an assumed density. Dividing by 6,000 cm³ per kg means the airline treats every 6,000 cm³ of space as if it weighed 1 kg, which is the same as 1 m³ = 166.67 kg. Cargo denser than that pays by actual weight; lighter cargo pays for the space it occupies. A divisor of 5,000 corresponds to 200 kg per m³. Sea freight uses a much heavier ratio, typically 1 m³ = 1,000 kg, because ships are limited more by weight than by volume.
Worked example
Default: 60 × 40 × 40 cm box, actual weight 12 kg, divisor 6,000.
- Volume: 60 × 40 × 40 = 96,000 cm³ = 96 L (shown as 0.1 m³ after rounding).
- Volumetric weight: 96,000 ÷ 6,000 = 16 kg.
- Compare: 16 kg is more than the actual 12 kg.
- Round up to 0.5 kg: 16 kg is already a multiple, so the chargeable weight is 16 kg.
With the courier divisor of 5,000, the same box would be 19.2 kg volumetric and charged as 19.5 kg.
How to read the result
If volumetric weight is well above actual weight, you are paying for air. A tighter box or splitting the shipment can lower the bill. If actual weight is higher, the box size hardly matters and only weight reduction helps. Always confirm which divisor and rounding rule your carrier applies, because both are set by each carrier's tariff.
Common mistakes
- Using inches with a metric divisor. Imperial formulas use a different divisor (for example 139 or 166 in³ per lb, depending on the carrier).
- Measuring the product instead of the outer carton, including bulges and handles.
- Assuming every carrier uses 6,000; express services often use 5,000.
Frequently asked questions
Why was my light parcel charged as a heavy one?
Because its volumetric weight was higher than its actual weight, and carriers bill the higher of the two.
What does 1:6000 mean?
That every 6,000 cm³ of package volume counts as 1 kg, or 166.67 kg per cubic meter.
Do carriers round the dimensions too?
Many round each dimension to the nearest or next whole centimeter before multiplying. Check your carrier's rule.
Sources: IATA, The Air Cargo Tariff and Rules (TACT), volume weight rules · Published service guides of major express carriers (dimensional weight sections)