Dimensional Weight (DIM Weight)
Also known as: DIM Weight, Volumetric Weight, Cubed Weight
Definition
Dimensional weight (also called DIM weight or volumetric weight) is a pricing method that calculates the “effective” weight of a package based on its size rather than its actual weight on a scale.
How It Works
Carriers use this formula to calculate dimensional weight:
DIM Weight = (Length × Width × Height) ÷ DIM Factor
The DIM factor for domestic packages:
- USPS: 139 (since July 12, 2026; previously 166)
- UPS: 139
- FedEx: 139
For example, a box measuring 18" × 12" × 10" with UPS:
- DIM Weight = (18 × 12 × 10) ÷ 139 = 15.5 lbs
If the actual weight is only 5 lbs, you’ll be charged for 16 lbs (rounded up).
Why Carriers Use DIM Weight
Shipping trucks and planes have two constraints: weight capacity and space. A truck full of pillows weighs very little but takes up the same space as a truck of bricks. DIM weight ensures carriers are compensated fairly for the space your package occupies.
Tips to Reduce DIM Weight Costs
- Use the smallest box possible - Don’t ship air; choose a box that fits your item snugly
- Consider poly mailers - For soft goods, mailers eliminate box dimensions entirely
- Flat rate options - USPS Flat Rate boxes ignore dimensions up to 70 lbs
- Compare carriers - Different DIM factors mean different prices for the same package
When DIM Weight Doesn’t Apply
- USPS parcels at or under 1 cubic foot (1,728 cubic inches)
- USPS Flat Rate boxes and envelopes
- Most freight/LTL shipments (they use freight class instead)