Dimensional (DIM) weight is a billing weight based on a package’s size: length x width x height divided by a divisor the carrier sets. Carriers charge the higher of the actual weight and the dimensional weight, so large, light packages are billed for the space they take.
This calculator shows actual, dimensional and chargeable weight side by side for one piece and for the whole shipment, using whichever divisor your carrier uses. Pick a common divisor or type your own.
Why Dimensional Weight Exists
A truck, van or aircraft runs out of space as well as weight. A box of pillows fills the same space as a box of books but weighs a fraction as much. Dimensional weight lets carriers charge for the space a light package takes, so that bulky, light shipments pay for the capacity they use.
How Do You Calculate Dimensional Weight?
- Measure length, width and height. Many carriers round each measurement up to the next whole inch.
- Multiply them to get the volume.
- Divide by the carrier’s divisor: in³ per lb for inches and pounds, or cm³ per kg for centimeters and kilograms.
- Compare the result with the actual weight. The higher number is the chargeable (billable) weight.
How RapidShips Calculates This
- Formula
- dimensional weight = L x W x H ÷ divisorchargeable weight = the higher of actual and dimensional weight
- Rounding
- With carrier rounding on, each dimension rounds up to the next whole unit and the dimensional weight rounds up to the next whole pound or kilogram, the method USPS publishes for its July 12, 2026 change.[1] The actual weight is rounded up the same way. Turn it off for exact values.
- Divisors
- Imperial divisors are in³/lb and metric divisors are cm³/kg. 6,000 cm³/kg is roughly 166 in³/lb; 5,000 cm³/kg is roughly 139 in³/lb.
- Limitations
- Carriers may apply minimum weights, size thresholds (USPS applies DIM weight to parcels over 1 cubic foot) and oversize charges. None of those are modeled.
Which Divisor Should You Use?
Carriers differ, and a contract can override the published number. These are the common starting points:
| Divisor | Units | Where you see it |
|---|---|---|
| 139 | in³ per lb | USPS since July 12, 2026 for parcels over 1 cubic foot;[1] also the figure major U.S. parcel carriers publish for most services |
| 166 | in³ per lb | The previous USPS divisor, and the imperial equivalent of 6,000 cm³/kg |
| 5,000 | cm³ per kg | Express services and some airlines[2] |
| 6,000 | cm³ per kg | The IATA industry standard for air cargo[2] |
Worked Example
A 20 x 16 x 12 in. box weighing 10 lb, divisor 139, with carrier rounding:
- Volume: 20 x 16 x 12 = 3,840 in³
- Dimensional weight: 3,840 ÷ 139 = 27.63, rounded up to 28 lb
- Chargeable weight: the higher of 10 lb and 28 lb = 28 lb
- With a 166 divisor the same box is 23.13, or 24 lb, which is why the divisor matters
Frequently Asked Questions
What is dimensional weight?
How do you calculate dimensional weight?
What divisor does USPS use for dimensional weight?
What is chargeable weight?
Does dimensional weight apply to LTL freight?
Related Freight Tools
Related Guides and Services
Sources
- USPS Postal Bulletin 22705, “Dimensional Weight (DIM) Changes, effective July 12, 2026,” accessed September 2026.
- Maersk, “Air cargo chargeable weight,” accessed September 2026.