FedEx Dimensional Weight Calculator
Calculate FedEx dimensional weight using the 139 in³/lb domestic divisor (5000 cm³/kg international), then compare it against actual weight to find the chargeable weight.
How FedEx dimensional weight works
FedEx bills the greater of actual weight and dimensional weight. Dimensional (DIM) weight converts a package's volume into a billable weight using a fixed divisor:
DIM weight = (L × W × H) ÷ divisor
For U.S. domestic FedEx Express and Ground the divisor is 139 in³/lb. For international shipments FedEx uses the metric 5000 cm³/kg divisor. Measure each side at its longest point, round each dimension to the nearest whole inch, multiply, divide by 139, then round the result up to the next whole pound.
Worked example (page defaults)
Take the default box of 20 × 15 × 10 in:
- Cubic size: 20 × 15 × 10 = 3,000 in³
- DIM weight: 3,000 ÷ 139 = 21.58, rounded up to 22 lb
If the parcel actually weighs 14 lb, FedEx bills the 22 lb dimensional figure because it is larger. The same box measured in centimetres (about 51 × 38 × 25 cm ≈ 48,450 cm³) divided by 5000 gives roughly 9.7, or 10 kg on the international divisor.
Divisor reference
| Carrier / service | Divisor | Unit |
|---|---|---|
| FedEx US domestic | 139 | in³/lb |
| FedEx international | 5000 | cm³/kg |
| UPS US daily rate | 139 | in³/lb |
| USPS (over 1 ft³) | 166 | in³/lb |
| Generic / older standard | 166 | in³/lb |
A smaller divisor produces a larger dimensional weight, so FedEx's 139 is less forgiving of light, bulky cartons than a 166-divisor service. Anything under one cubic foot is typically exempt from DIM pricing on domestic ground, but always confirm the current threshold with FedEx.
Lowering the chargeable weight
Because the divisor is fixed, the only lever you control is volume. Trimming void space, choosing a snug box, or splitting one oversized carton into two right-sized ones can move you from the dimensional figure back to actual weight. To see the comparison side by side, use the chargeable weight calculator; to test another courier's number, the UPS dimensional weight calculator uses the same 139 divisor, while the generic dimensional weight calculator lets you switch divisors freely. For the underlying concept, see dimensional weight explained.