For the underlying carrier rule this is based on, see a pricing method used industry-wide, including by IATA for air cargo: Volumetric weight.
Part of: Dimensional weight
Volumetric weight — sometimes called dimensional weight or DIM weight — is the weight a carrier bills you on when your package is large but light. The formula is the same everywhere: length × width × height ÷ a carrier divisor. Carriers then bill on whichever is greater, actual weight or that dimensional figure.
Try the Calculator
Enter your package dimensions and (optionally) actual weight. The calculator returns the dimensional figure at both common divisors and shows the billable weight a carrier would charge you on.
The Volumetric Weight Formula
The math is the same on every carrier — only the divisor changes:
Volumetric weight = (length × width × height) ÷ divisor
For US domestic shipments, measure dimensions in inches and use a divisor of 139 — the result is in pounds. For international shipments measured in centimeters, use 5,000 — the result is in kilograms. Round the dimensions up to the nearest whole inch (or centimeter) before multiplying, the way carriers do, and round the final figure up to the nearest whole unit. That rounded number is what the carrier bills on if it is greater than the package’s actual weight.
Carrier Divisor Reference Table
Most national carriers settled on a divisor of 139 in³/lb for US domestic packages and 166 in³/lb for international export, with the metric equivalents of 5,000 cm³/kg for air and 6,000 cm³/kg for ground / road freight. USPS is the outlier — it only applies volumetric pricing to Priority Mail packages above 1 cubic foot.
| Carrier | US domestic divisor | International divisor | When it applies |
|---|---|---|---|
| UPS | 139 in³/lb | 139 in³/lb (export); 5,000 cm³/kg | All Ground, Air, and Worldwide Express packages |
| FedEx | 139 in³/lb | 139 in³/lb (Express); 5,000 cm³/kg | All FedEx Express, Ground, and Home Delivery packages |
| USPS | 166 in³/lb | n/a (international uses different rate sheets) | Priority Mail & Priority Mail Express packages over 1 cubic foot (1,728 cu in) to Zones 1–9 |
| DHL Express | 139 in³/lb (US eCommerce); 166 (legacy lanes) | 5,000 cm³/kg (Express); 166 in³/lb | All international Express shipments and most US-domestic eCommerce |
Carriers re-publish their official DIM divisors in their annual rate guides — check the current carrier rate sheet before quoting a high-stakes shipment, since divisor changes happen at every January rate cycle.
Actual Weight vs. Dimensional Weight
Actual weight is what the box weighs on a scale. Dimensional weight is what the box would weigh if it were filled with something of average density. Carriers bill on the greater of the two — that number is called the billable weight (or “chargeable weight” on international air waybills).
Example: a 24 in × 18 in × 12 in box of pillows weighs 8 lb on the scale.
| Calculation | Math | Result |
|---|---|---|
| Volume | 24 × 18 × 12 | 5,184 cu in |
| Dimensional weight (divisor 139) | 5,184 ÷ 139 | 37.3 lb → 38 lb billable |
| Dimensional weight (divisor 166) | 5,184 ÷ 166 | 31.2 lb → 32 lb billable |
| Actual weight | 8 lb | 8 lb |
| Billable weight (UPS / FedEx domestic, divisor 139) | max(8, 38) | 38 lb |
The pillows weigh 8 lb but are billed at 38 lb — almost five times the actual weight. The fix is not to dispute the bill; it is to right-size the box. Dropping the box from 24 × 18 × 12 to 18 × 14 × 10 (2,520 cu in) cuts the dimensional figure to 18.1 lb at divisor 139 — 20 lb billable instead of 38, with no change to the contents.
How to Avoid DIM Weight Surcharges
- Use the smallest box that fits the contents. Every extra inch of empty space pays carrier billing.
- Skip dunnage you do not need. Air pillows, foam, and oversized boxes look protective but they pay on dimensional weight regardless.
- Compress soft goods. Vacuum bags, roll-pack bedding, and ship-in-original-packaging strategies all reduce billable cube.
- Quote both divisors before booking. A package that exceeds USPS’s 1 cubic foot threshold often costs more on USPS Priority than on UPS Ground for the same weight — the divisors flip the math.
- Run the rate comparison. Use the shipping calculator to see all four carriers side-by-side at commercial rates — the cheapest carrier on a heavy box is rarely the cheapest carrier on a big-but-light box.
Dimensional Weight Around the Silo
- Compare carriers on this exact package: the ParcelPath shipping calculator applies the right divisor per carrier and returns commercial-rate quotes side-by-side.
- Dimensional weight reference: see our dimensional weight calculator for the US-domestic-focused view of the same math (DIM is the older industry term for the same metric).
- Carrier-by-carrier rules: each national carrier publishes its own DIM-weight policy — the shipping companies overview links to UPS, USPS, FedEx, and DHL rate guides.
What is volumetric weight?
How do I calculate dimensional weight in pounds?
What divisor do UPS and FedEx use for DIM weight?
Does USPS charge dimensional weight?
What is the difference between volumetric weight and dimensional weight?
Why do carriers charge by dimensional weight instead of actual weight?
This page is part of the ParcelPath shipping calculator hub — quote all four national carriers at commercial rates before you ship.
Part of our Calculate Postage guide. Related: Dimensional Weight, International, Ebay Shipping Calculator.
