Dimensional Weight Calculator
Enter your box size and pick a carrier divisor to get the dimensional (volumetric) weight and the chargeable weight you'll be billed on.
How dimensional weight works
Carriers bill a parcel on whichever is larger: its actual weight or its dimensional weight (also called DIM or volumetric weight). Dimensional weight converts the space a box occupies into a billable weight, so a light but bulky carton is not shipped at a giveaway figure.
The formula is simply volume divided by a divisor:
dimensional weight = (L × W × H) ÷ divisor
This page uses the generic / standard divisor of 166 in³/lb (the imperial equivalent of 5000 cm³/kg). Smaller divisors penalise volume more; the 166 figure is the common baseline before a specific carrier's number is applied. The result is rounded up to the next whole pound by most carriers.
Worked example (page defaults)
Take the default box of 20 × 15 × 10 in:
- Cubic size:
20 × 15 × 10 = 3,000 in³ - Dimensional weight:
3,000 ÷ 166 = 18.07 lb - Rounded up: 19 lb
If the box actually weighs 14 lb, you are billed on the 19 lb dimensional figure because it is greater. If it weighs 25 lb, the actual weight wins and DIM is ignored. That comparison is the whole point of the chargeable weight calculator.
Divisor reference
Different carriers and modes apply different divisors. Larger divisor = lighter dimensional weight for the same box.
| Carrier / mode | Imperial (in³/lb) | Metric (cm³/kg) |
|---|---|---|
| Generic / standard | 166 | 5000 |
| FedEx (US domestic) | 139 | 5000 |
| UPS (daily rate domestic) | 139 | 5000 |
| USPS (over 1 ft³) | 166 | - |
| DHL Express | ~139 | 5000 |
| Air freight (IATA) | ~166 | 6000 |
The lower 139 divisor used by FedEx and UPS produces a higher dim weight than the 166 baseline for the same carton, our 3,000 in³ example becomes 3,000 ÷ 139 = 21.6 → 22 lb instead of 19 lb.
How to lower dim weight
Because the divisor is fixed, the only lever you control is volume. Right-sizing the carton, removing void fill, and avoiding oversized boxes all cut L × W × H and therefore the dimensional weight. If you ship by the cubic metre rather than the parcel, work in CBM first with the CBM calculator, and for metric courier billing use the volumetric weight calculator. For palletised LTL freight, the figure that drives class is density rather than a divisor, see the freight density calculator.