Shipping & packaging
How Dimensions and Weight Are Rounded for DIM Pricing
Two packages a fraction of an inch apart can bill a whole pound or kilogram apart, because measurements and weights are often rounded before a price is looked up. Seeing where the rounding happens explains why the figure a carrier bills on can be higher than a calculator’s exact result.
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Rounding the dimensions
Some carriers round each dimension — commonly up to the next whole inch or centimeter — before multiplying. A 17.25 × 13.5 × 9.6 in box is 2,235.6 in³, or 16.08 lb at 139. Rounded up to 18 × 14 × 10 in, it is 2,520 in³, or 18.13 lb: over 2 lb more from rounding alone.
Rounding the weight
Dimensional and actual weights are commonly rounded up too. The same 16.08 lb becomes 17 lb at whole-pound rounding, or 16.5 lb at half-pound rounding. Rounded dimensions plus rounded weight takes that box from 16.08 lb exact to 19 lb billed.
| Rounding applied | DIM weight |
|---|---|
| None | 16.08 lb |
| Weight up to the next half pound | 16.5 lb |
| Weight up to the next whole pound | 17 lb |
| Dimensions and weight up to whole units | 19 lb |
A metric example
A 41.2 × 31.5 × 20.4 cm box is 26,475 cm³, or 5.30 kg at 5,000. Rounded up to the next half kilogram it is 5.5 kg; to the next whole kilogram, 6 kg. With each dimension rounded up to 42 × 32 × 21 cm first, it is 5.64 kg, which rounds to 6 kg either way.
What to confirm with your carrier
- Whether dimensions are rounded, and whether up or to the nearest unit.
- Whether weights are rounded to whole or half units.
- Whether the same rounding applies to the actual weight.
- How bulging or irregular packages are measured.
DIM Rounding Explained FAQ
- Do carriers round dimensions up or to the nearest inch?
- It varies. Many round up to the next whole inch or centimeter, but check your carrier’s current rules.
- Why is my billed weight higher than the calculator’s exact figure?
- Rounding. Rounding dimensions and weights up can add more than a pound, as the 17.25 × 13.5 × 9.6 in example shows.
- Is actual weight rounded too?
- Usually it is rounded the same way as the dimensional weight before the two are compared.
- What is half-pound rounding?
- Rounding a weight up to the next 0.5 lb, so 16.08 lb becomes 16.5 lb rather than 17 lb.
- Can rounding make two different boxes bill the same?
- Yes. Boxes whose rounded dimensions or weights land on the same whole unit bill the same, even if they differ slightly.
Related guides
- What Is a DIM DivisorWhat a dimensional-weight divisor is, why it has units, how it turns box volume into a weight, and why a larger divisor gives a lower DIM weight.
- DIM Divisors ComparedHow the common DIM divisors 139 and 166 in³/lb and 5,000 and 6,000 cm³/kg compare, how to convert between them, and one box worked out with each.
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