Dimensional weight vs actual weight: which one is billed?
The carrier bills the higher of the two, after rounding up to its weight step. A light, bulky carton is billed on its volume; a dense one on its scale weight.
- Billable weight
- The higher of actual and dimensional weight, rounded up to the carrier’s step
- Dimensional weight
- Length × width × height ÷ divisor (5000 cm³/kg or 139 in³/lb for most express parcels)
- Billed on volume when
- Lighter than 200 kg/m³ at 5000, about 12.43 lb/ft³ at 139
- Exception
- USPS applies dimensional weight only over 1,728 in³
Three cartons, one rule
Actual weight is what the scale shows. Dimensional (volumetric) weight is length × width × height ÷ the divisor. With 5000 cm³/kg and 0.5 kg steps:
| Carton | Size (cm) | Scale (kg) | Volumetric (kg) | Billed (kg) | Billed on |
|---|---|---|---|---|---|
| Light and bulky | 40 × 30 × 25 | 4 | 6 | 6 | Volume |
| Heavy and compact | 30 × 25 × 20 | 9.5 | 3 | 9.5 | Scale weight |
| Same step either way | 21 × 20 × 50 | 4.1 | 4.2 | 4.5 | Either (same step) |
- Light and bulky. 30,000 cm³ ÷ 5000 = 6 kg, above the 4 kg on the scale, so 6 kg is billed: 2 kg of air.
- Heavy and compact. The volumetric weight is only 3 kg, so the 9.5 kg scale weight is billed. A smaller box would change nothing.
- Same step either way. The volumetric weight, 4.2 kg, is a little above the 4.1 kg scale weight, but both round up to 4.5 kg. The box is not costing you anything extra, so shrinking it would not lower the bill.
Open these three cartons in the calculator
A quick density check
Under 5000 cm³/kg a carton is billed on volume when it weighs less than 200 kg per cubic metre of box. With the US 139 in³/lb rule the line is about 12.43 lb per cubic foot. Below that, you are paying for air; above it, the scale weight counts.
When dimensional weight does not apply at all
Some rules only use dimensional weight above a size. From 12 July 2026, USPS applies it only to parcels over 1,728 in³ (one cubic foot) after each side is rounded up to a whole inch. A 30 × 25 × 20 cm box weighing 1 kg becomes 12 × 10 × 8 in = 960 in³, so USPS bills the scale weight, even though the box is light: 1 kg is 2.2 lb, rounded up to 3 lb. See the USPS calculator.
Billable weight is not the price
Two cartons with the same billable weight can still cost different amounts: zone, service, fuel surcharge, oversize or additional handling charges and your contract all change the final charge. Billable weight is the weight the price is looked up for.
Related
Last updated: 28 October 2026. Billable weight only: surcharges, minimum charges and your negotiated rates are not included.