Shipping Weight Calculator
Carriers Bill on Size as Often as They Bill on Scale
A box of pillows and a box of textbooks can weigh wildly different amounts while taking up the same space on a truck or in an aircraft cargo hold. Because cargo space is the real constraint, carriers calculate a "dimensional weight" from a package's size and charge based on whichever is larger — the actual weight on the scale or the dimensional weight from the tape measure.
The Formula
Billable Weight = MAX(Actual Weight, Dimensional Weight)
The divisor depends on the carrier and service level. Smaller divisors produce a higher dimensional weight for the same box, so express and international services — which use larger divisors like 166 rather than 139 — are comparatively more forgiving of bulky, lightweight packages.
Standard Carrier Divisors
| Service type | Units | Divisor |
|---|---|---|
| Standard domestic | inches → lb | 139 |
| Express / international | inches → lb | 166 |
| Metric standard | cm → kg | 5,000 |
| Metric express | cm → kg | 6,000 |
An 18 × 14 × 12 in box (3,024 in³) works out to 21.76 lb dimensional weight on the standard divisor, versus 18.22 lb on the express divisor — the same box, two different billed weights.
Where This Matters
- Packaging design — shrinking a box's dimensions, not just its weight, directly lowers the billed rate for light, bulky items.
- Carrier and service comparison — the cheaper-looking rate can lose once its divisor produces a higher dimensional weight on your typical package mix.
- Budgeting for e-commerce fulfillment — knowing the billable weight in advance avoids invoice surprises when packaging is oversized relative to product weight.
How to Use This Calculator
- Enter the Actual Weight of the package.
- Enter Length, Width, and Height.
- Select the carrier Divisor matching your service — Standard Domestic, Express/International, Metric Standard, or Metric Express.
- Select Calculate to see the billable weight and whether it was set by actual or dimensional weight.
Related Calculations
Run the same math with a custom divisor using the Dimensional Weight Calculator, or turn a billable weight into a price with the Freight Cost Calculator.