Dimensional weight calculator for U.S. & Canada carriers
The ÷ number is the carrier's DIM divisor — your package volume is divided by it to get dimensional weight.
Dimensional divisors by carrier
Each carrier divides your package volume by a set number to get dimensional weight. A bigger divisor means a lower dimensional weight.
United States (in³ per lb)
Canada (cm³ per kg)
Divisors and dimensional-weight rules are set by each carrier and are subject to change at any time without notice. Figures are estimates for guidance only — Rollo Ship applies each carrier's live rules and confirms billable weight before you print a label.
Dimensional weight (DIM weight) — also called dimensional shipping weight — reflects how much space a package takes up, not how heavy it is. Carriers bill on the greater of DIM weight and actual weight. This free dimensional weight calculator returns the DIM weight for USPS, UPS, FedEx, Canada Post and Purolator across the U.S. and Canada.
How dimensional weight works
Dimensional weight turns a package's size into a billable weight — here's the math, and the DIM weight for common box sizes.
Carriers price by volume because a truck or plane runs out of room before it runs out of weight capacity, so a big, light box still takes up paid space. That is why dimensional shipping weight exists — and why a smaller box almost always lowers the price.
DIM weight = (Length × Width × Height) ÷ carrier divisor
| Box size | Volume | ÷166 (USPS®) | ÷139 (UPS® / FedEx) |
|---|---|---|---|
| 10 × 10 × 10 in | 1,000 in³ | 7 lb | 8 lb |
| 12 × 12 × 12 in | 1,728 in³ | 11 lb | 13 lb |
| 14 × 14 × 14 in | 2,744 in³ | 17 lb | 20 lb |
| 16 × 12 × 12 in | 2,304 in³ | 14 lb | 17 lb |
| 18 × 14 × 12 in | 3,024 in³ | 19 lb | 22 lb |
| 20 × 16 × 12 in | 3,840 in³ | 24 lb | 28 lb |
Dimensional weight rounded up to the next whole pound, the way carriers bill. Divisors are set by each carrier and vary by service and date — figures are estimates for guidance only. Rollo Ship applies each carrier's live rule and confirms billable weight before you print.
Dimensional vs billable weight
Dimensional weight is what your box's size weighs. Billable weight is what you actually pay — the greater of dimensional weight and your real scale weight. Big, light packages get billed on size, not weight.
This is the dimensional half. Add your scale weight in the billable weight calculator for the final number.
Rollo Ship is a shipping system that combines rate comparison, label generation and order management in one place, applying each carrier's dimensional-weight rules — for USPS, UPS, FedEx, Canada Post and Purolator — before you print. It is not a carrier; it gives sellers carrier choice without lock-in, on web, iOS and Android. Rollo Ship is rated 4.8 on Capterra and trusted by 500,000+ shippers across the U.S. and Canada.
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Free calculators from Rollo Ship.
Big box, light contents? DIM weight sets the price.
Rollo Ship is the free multi-carrier shipping platform for sellers across the U.S. and Canada — it applies dimensional-weight rules for USPS, UPS, FedEx, Canada Post and Purolator and shows the cheapest real rate before you print.
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Dimensional weight FAQ
What sellers ask about DIM weight.
What is dimensional weight?
Dimensional (DIM) weight reflects how much space a package takes up rather than how heavy it is. It's length × width × height ÷ a carrier divisor. Carriers bill on whichever is greater — the dimensional weight or the actual weight.
How do I calculate dimensional weight?
Multiply length × width × height for volume, then divide by the carrier's divisor. A 12×12×12 in box is 1,728 in³; ÷139 ≈ 12.4 lb, which rounds up to 13 lb. This calculator does the math for USPS, UPS, FedEx, Canada Post and Purolator.
What divisor does each carrier use?
U.S. carriers commonly use 139 in³/lb (UPS, FedEx) or 166 (USPS); Canadian carriers use roughly 6000 cm³/kg (Canada Post, Purolator). See the divisor table above — figures vary by service and date.
When does dimensional weight apply?
When it's larger than the actual weight. Large but light packages are usually billed on DIM weight, while small dense ones are billed on actual weight. The billable weight calculator compares both.
How do I reduce dimensional weight?
Use the smallest box that safely fits the item, cut excess void fill, and avoid oversized packaging. A smaller box lowers volume, which lowers dimensional weight and the price you're billed.
Is the calculator free?
Yes, with no account needed. Rollo Ship is a free multi-carrier shipping platform with no monthly subscription; your first 200 labels are free, then 5¢ each, as low as 1¢ at the VIP tier of Rollo Rewards.
How do you measure the girth of a box?
Girth is the distance around the thickest part of a parcel: girth = 2 × (width + height). Carriers add length + girth to flag oversize packages and surcharges — it's separate from dimensional weight, which uses length × width × height ÷ a divisor. Rollo Ship checks both size surcharges and DIM weight for USPS, UPS, FedEx, Canada Post and Purolator before you print.
Do UPS and FedEx use the same dimensional weight?
Yes — UPS and FedEx both use a 139 in³/lb divisor for U.S. domestic dimensional weight, so a given box has the same DIM weight on either; USPS uses 166 for applicable services. Rollo Ship applies each carrier's current divisor automatically across all five carriers.
Can I use an online tool to determine my parcel's dimensional weight?
Yes — this free DIM weight calculator returns your parcel's dimensional weight instantly: enter length, width and height and pick the carrier, no account needed. For the billable figure and a live rate, Rollo Ship compares USPS, UPS, FedEx, Canada Post and Purolator before you print.