What Is Dimensional Weight? How Carriers Charge by Box Size (2026)
By Saurabh Pandey · Updated · 3 min read
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If you have ever paid to ship a pillow and been charged for 15 pounds, you have met dimensional weight. Carriers price parcels by the space they take up in a truck or plane, not only by what they weigh. For online sellers with light, bulky products, it can be the biggest hidden shipping cost.
What dimensional weight means
Dimensional weight (also called volumetric or DIM weight) is a weight calculated from the size of a parcel. Carriers compare it with the actual weight and charge for whichever is greater. That greater figure is called the billable weight.
The formula is the same everywhere; only the divisor changes:
Dimensional weight = length × width × height ÷ divisor
Measure in inches to get pounds, or in centimetres to get kilograms. Measure the box at its widest points, including bulges, and round each side up to the next whole unit, as carriers do.
Each carrier's divisor
| Carrier | Divisor | Notes |
|---|---|---|
| UPS (daily rates) | 139 (in → lb) | Most business accounts |
| UPS (retail rates) | 166 | Prices at UPS stores |
| FedEx | 139 | US and international |
| USPS | 166 | Only for parcels over 1 cubic foot (1,728 cubic inches) |
| DHL Express | 5,000 (cm → kg) | International express |
| Amazon FBA | 139 | Used to set FBA fee tiers and weights |
A smaller divisor means a higher dimensional weight, so UPS and FedEx daily rates (139) are stricter than USPS (166). Try your own boxes:
Dimensional Weight Calculator
Open full calculatorFee breakdown
Enter the box dimensions.
Worked examples
An 18 × 12 × 10 inch box weighing 3 lb. The volume is 2,160 cubic inches.
- With UPS daily rates: 2,160 ÷ 139 = 15.5 lb, rounded up to 16 lb. You pay for 16 lb, not 3.
- With USPS: the box is over one cubic foot, so 2,160 ÷ 166 = 13.0 lb, rounded up to 14 lb.
A 16 × 12 × 8 inch box weighing 3 lb with FedEx. 1,536 ÷ 139 = 11.05, so it is billed as 12 lb. Using a 14 × 10 × 6 inch box instead, if the product fits, drops the billable weight to 7 lb.
A 40 × 30 × 20 cm parcel weighing 3 kg with DHL Express. 24,000 ÷ 5,000 = 4.8 kg, which DHL rounds up to 5 kg.
The live table of divisors we use, with links to each carrier's rules:
| Carrier | Imperial | Metric | Rule |
|---|---|---|---|
| UPS (daily rates) | L × W × H ÷ 139 (inches → lb) | ÷ 5,000 (cm → kg) | Rounded up to the next lb |
| UPS (retail rates) | L × W × H ÷ 166 (inches → lb) | ÷ 6,000 (cm → kg) | Rounded up to the next lb |
| FedEx | L × W × H ÷ 139 (inches → lb) | ÷ 5,000 (cm → kg) | Rounded up to the next lb |
| USPS (Priority, Ground Advantage) | L × W × H ÷ 166 (inches → lb) | ÷ 6,000 (cm → kg) | Rounded up to the next lb; only over 1 cubic foot |
| DHL Express (international) | L × W × H ÷ 139 (inches → lb) | ÷ 5,000 (cm → kg) | Rounded up to the next 0.5 kg |
| DHL eCommerce (US) | L × W × H ÷ 166 (inches → lb) | ÷ 6,000 (cm → kg) | Rounded up to the next lb |
| Amazon FBA fee tiers | L × W × H ÷ 139 (inches → lb) | ÷ 5,000 (cm → kg) | Not rounded |
Billable weight is the greater of actual and dimensional weight. USPS only applies dimensional weight to parcels larger than 1 cubic foot (1,728 cubic inches). Amazon assumes a minimum width and height of 2 inches for bulky items.
Last verified: . Official sources: UPS: shipping dimensions and weight · FedEx: what is dimensional weight? · USPS: parcel size, weight & fee standards · USPS Domestic Mail Manual 223 · DHL eCommerce: chargeable weight
Why USPS can be cheaper for small boxes
USPS only applies dimensional weight to parcels larger than one cubic foot. A 12 × 12 × 12 inch box is exactly 1,728 cubic inches, so with USPS it is charged by actual weight, while UPS and FedEx would bill a 5 lb box in it as 13 lb. For light products that fit in boxes up to one cubic foot, USPS is often the cheapest option.
Dimensional weight on Amazon
Amazon uses dimensional weight to decide an item's FBA size tier and shipping weight. For large standard and bulky items, the shipping weight is the greater of the unit weight and the dimensional weight (volume ÷ 139), with a minimum width and height of 2 inches for bulky items. A product measured a little too large can move into a more expensive tier, so check the dimensions Amazon records in Seller Central. The Amazon FBA calculator shows what each tier costs.
How to stop paying to ship air
- Use the smallest box that protects the product. A 12-inch cube is 1,728 cubic inches; an 11-inch cube is 1,331, almost a quarter smaller.
- Ship soft goods in poly mailers. Clothing, textiles and plush items compress well.
- Stock a few box sizes that match your best-selling products.
- Compare carriers for each box size. USPS for boxes up to one cubic foot, UPS or FedEx for heavier, denser parcels.
- Charge enough shipping. On marketplaces that charge fees on shipping, undercharging costs you twice. Check with the Etsy or eBay calculator.
The bottom line
Dimensional weight means box size matters as much as weight. Know each carrier's divisor, measure honestly, use smaller boxes and mailers where you can, and check every new product with the dimensional weight calculator before setting its shipping price.
Divisors and rules in this guide were checked against UPS, FedEx, USPS, DHL and Amazon pages in October 2026. Your negotiated rates may use different divisors.
Frequently asked questions
How do I calculate dimensional weight?
Multiply length × width × height in inches and divide by 139 (UPS daily rates, FedEx) or 166 (USPS, UPS retail). In centimetres, divide by 5,000 to get kilograms for DHL Express and most international express services.
Does USPS use dimensional weight?
Yes, but only for parcels larger than one cubic foot sent by Priority Mail, Priority Mail Express, Ground Advantage or Parcel Select. USPS divides by 166 and rounds up to the next pound.
What is billable weight?
The weight you are charged for: the greater of the parcel's actual weight and its dimensional weight.
Is dimensional weight rounded up?
UPS, FedEx and USPS round up to the next whole pound, and DHL Express to the next half kilogram. Each side is usually measured and rounded up to the next whole inch or centimetre first.