Shipping
Dimensional weight calculator
Calculate dimensional (DIM) and volumetric package weight, compare actual versus billable weight, and check standard divisors for FedEx, UPS, USPS, and DHL.
Dimensional weight divisors by carrier
The divisor, not the tape measure, decides whether a light box is billed as a heavy one.
Updated 2026-09-07.
What DIM weight is
Couriers convert volume to a billable weight so air and van space is not given away to light, bulky cartons. You pay the greater of the scale weight and the dimensional weight. The conversion is volume divided by a divisor the carrier publishes for that product.
| Product (typical) | Inches divisor | Cm divisor |
|---|---|---|
| FedEx Express/Ground | 139 | 5000 |
| UPS daily / commercial | 139 | 5000 |
| UPS retail / UPS Store | 166 | 6000 |
| USPS Priority (over 1 cu ft) | 166 | 6000 |
| DHL Express | 139 | 5000 |
| IATA air cargo rule of thumb | 166 | 6000 |
Royal Mail is not in this table
UK consumer Letter and Parcel products use maximum centimetres and grams, not L×W×H/divisor. Do not DIM a Large Letter. Use the parcel size checker for Royal Mail; use the dimensional weight calculator for FedEx, UPS, DHL, and similar.
How to use the divisor
Measure the boxed outer inches or centimetres. Multiply the three sides. Divide by the preset. Compare to the scale weight. The calculator rounds in the usual billable direction for the unit system you picked.
Contract accounts sometimes get a different divisor than walk-up retail. If your invoice disagrees, the invoice’s divisor is the one that was applied.
Related tools
Shipping
UK parcel size checker
Check parcel dimensions and weight against UK carrier and Royal Mail bands (Letter, Large Letter, Small Parcel, Medium Parcel).
Related guides
Shipping
Royal Mail Large Letter vs Small Parcel
The thickness cap on Large Letter is 25 mm. Miss it and Royal Mail consumer postage steps up to Small Parcel.
Dimensional weight divisors by carrier FAQ
- Why is 139 ‘more expensive’ than 166?
- A smaller divisor produces a higher DIM weight from the same box, so more shipments hit volumetric billing.