Volumetric weight: why a light box costs more than it weighs
You weighed the parcel at 3 kilograms, then the shipping bill came in at 4.8. The carrier did not get it wrong. The box takes up more room in the plane or truck than its weight suggests.
What volumetric weight is
Carriers work out two weights for a parcel: the actual weight on the scale, and the volumetric weight calculated from the box dimensions. They charge you for whichever is larger, called the “chargeable weight”. That way a big box full of padding cannot take up lots of space at the price of a small parcel.
The formula
Volumetric weight in kg = length × width × height in cm ÷ divisor.
The divisor is set by the carrier. Common values are 5000 and 6000 for centimeters and kilograms. Each carrier publishes its own, and it can differ between services, so ask yours.
A 40 × 30 × 20 cm box, actual weight 3 kg.
Volume: 24,000 cm³.
With a divisor of 5000: volumetric weight 4.8 kg, so 4.8 kg is charged.
With a divisor of 6000: volumetric weight 4 kg, so 4 kg is charged.
A 30 × 20 × 10 cm box, actual weight 2.5 kg.
Volumetric weight with a 5000 divisor is 1.2 kg.
The actual weight is larger here, so 2.5 kg is charged.
How to do it
- Open the Volumetric shipping-weight calculator.
- Type the length, width and height, and choose centimeters or inches.
- Type the actual weight and choose the divisor your carrier uses.
- You see all three weights and which one is charged. Enter a number of parcels to get the total.
How to lower the chargeable weight
- Use the smallest box that fits the product safely. Every extra centimeter in each direction grows the volume fast.
- Measure the box at its widest points, because carriers do. A bulging box is bigger than you think.
- If your products are light and bulky, compare carriers with different divisors. As you saw, the gap between 5000 and 6000 is not small.
What the tool does not do
The tool calculates weights only. It knows no carrier's prices. It also does not apply rounding rules some carriers use, like rounding weight up to the next half kilogram, so your bill may show a slightly higher weight. Once you know your real shipping cost, build it into your price with the Selling-price calculator, and prepare the parcel contents list with the Packing-list generator.
Common questions
Which divisor is right?
There is no single right divisor. The values in the tool are common but not tied to any carrier, so use the one your carrier publishes.
Does it support inches and pounds?
Yes, with common divisors such as 139 and 166, and exact unit conversion.
What about irregular parcels?
The tool assumes a rectangular box. For irregular parcels use the extreme dimensions, as most carriers do.