Dimensional Weight Calculator — UPS, FedEx, USPS & Amazon FBA
Dimensional weight (DIM weight) is a pricing method used by parcel carriers to account for packages that are large but lightweight. Instead of billing only by actual weight, carriers calculate a “dimensional weight” based on your package size — and charge whichever is higher. This means an oversized box with a light product inside can cost significantly more than a compact, well-fitted package. Use our free calculator to check your DIM weight across UPS, FedEx, USPS, and Amazon FBA instantly.
Dimensional Weight Calculator
Enter your package dimensions to calculate DIM weight for UPS, FedEx, USPS, and Amazon FBA. Carriers bill whichever is greater — actual weight or dimensional weight.
Package dimensions
Actual weight
What is dimensional weight?
Dimensional weight (also called DIM weight or volumetric weight) is a pricing method where carriers calculate a hypothetical weight based on the size of your package rather than its actual weight. The formula is length × width × height (in inches) divided by a carrier-specific divisor. Carriers bill whichever is greater — actual weight or DIM weight — because they need to account for the space a package takes up in their trucks and planes, not just its heaviness.
What is a DIM divisor?
The DIM divisor (also called the DIM factor) is the number used to convert cubic inches into pounds. UPS, FedEx, and Amazon FBA use a divisor of 139 for both domestic and international shipments. USPS uses a more generous divisor of 166 for Priority Mail and Priority Mail Express, which means USPS assigns a lower DIM weight for the same package size. A lower divisor produces a higher DIM weight (worse for you), while a higher divisor produces a lower DIM weight (better for you).
How do I reduce my DIM weight?
The most effective way to reduce DIM weight is to use the smallest box that safely fits your product. Eliminate excess void fill, consider custom-sized boxes instead of standard sizes, and remove unnecessary inner packaging. Even reducing one dimension by an inch can meaningfully lower your DIM weight. If you ship high volumes, you may also be able to negotiate a higher DIM divisor (like 166 or 194) with UPS or FedEx, which lowers the calculated DIM weight.
Do all carriers use the same DIM divisor?
No. UPS and FedEx both use 139 for domestic and international shipments. USPS uses 166 for Priority Mail and Priority Mail Express, making it more forgiving for larger, lighter packages. Amazon FBA uses 139 for calculating fulfillment fees. Some carriers offer negotiated divisors for high-volume shippers — ask your account representative.
When does DIM weight apply?
DIM weight applies to most parcel shipments with UPS and FedEx regardless of size. For USPS, DIM weight applies to Priority Mail packages over 1 cubic foot (1,728 cubic inches) — smaller packages are billed by actual weight only. For LTL freight shipping, carriers use density-based freight classes instead of DIM weight. The rules differ by carrier, so always check current carrier guidelines.
What is the DIM weight formula?
The formula is: (Length × Width × Height in inches) ÷ DIM divisor = DIM weight in pounds. For example, a box measuring 20 × 14 × 10 inches with UPS: (20 × 14 × 10) ÷ 139 = 20.1 lbs DIM weight, rounded up to 21 lbs. If your actual package weighs 12 lbs, UPS will bill you for 21 lbs because the DIM weight is higher.
Can I negotiate my DIM divisor with carriers?
Yes, if you ship significant volume. Large shippers often negotiate DIM divisors of 166, 194, or even higher with UPS and FedEx, which reduces their DIM weight charges. Contact your carrier account representative or freight broker to discuss volume-based pricing. Even moving from 139 to 166 can mean significant savings on lightweight, bulky products.
This calculator provides estimated dimensional weights based on currently published carrier divisors. Actual billing may differ based on negotiated rates, carrier-specific rules, package minimums, and surcharges. DIM divisors and carrier policies are subject to change. USPS DIM pricing applies only to Priority Mail packages over 1 cubic foot. Always confirm pricing with your carrier or shipping platform before committing to shipment costs. National Freight Hub is not liable for billing differences resulting from use of this tool.