How dimensional weight works
Dimensional weight (DIM) is how carriers charge for boxes of air. If the size-based weight is higher than the scale weight, you often pay the size-based number.
The idea in one sentence
A 1 lb item in a huge carton takes the same truck space as a heavier item in that carton — so the carton can price as if it were heavier.
Typical formula
DIM pounds = ceil(L × W × H ÷ divisor). USPS commonly uses 166 and often starts applying DIM when volume is over 1 cubic foot. UPS daily rates often use 139. These are planning defaults, not a contract. Confirm with a live quote.
How to pay less without cheating
- Use a smaller box or a mailer.
- Cut down a carton rather than filling it with pillows of air.
- Do not under-declare inches. Adjustments cost more than honest DIM.
Try the dimensional weight calculator, then compare shipping rates.
Keep reading
Frequently asked questions
Compare live rates
The quote applies the carrier’s current DIM rule for you.