Ecommerce · 28 Oct 2026
How to calculate profit margin (gross, operating and net)
Profit margin = profit ÷ revenue × 100. Here is how to calculate gross, operating and net margin, with worked examples, Excel formulas and 2026 benchmarks.
Key takeaways
- Dimensional weight = L × W × H ÷ divisor. Carriers bill the higher of dimensional weight and actual weight.
- In inches the divisor is 139 at UPS daily rates, FedEx and, since 12 July 2026, USPS. In centimetres it is 5,000 at UPS, FedEx and DHL Express.
- An 18 × 14 × 10 inch box holding a 6 lb order bills at 19 lb. The box size is the part of the formula you control.
Dimensional weight is the weight a carrier charges for the space a parcel takes up. To calculate it, multiply length × width × height and divide by the carrier's divisor. In inches the answer is in pounds; in centimetres it is in kilograms. The carrier then bills whichever is higher: the dimensional (DIM) weight or the weight on the scale. That higher number is the billable weight.
Outside the US the same idea is usually called volumetric weight. The maths is identical; only the units and divisors change. Below you will find the formula, the 2026 divisors for each major carrier, worked examples and the quickest ways to stop paying to ship air.
The dimensional weight formula
Every parcel carrier uses the same formula. What changes is the divisor and how each side is rounded.
- Measure the outside of the packed box: the longest side is length, then width, then height. Include bulges and flaps.
- Round each side up to the next whole inch (or centimetre). UPS, FedEx and now USPS all round up, so 12.1 inches counts as 13.
- Multiply length × width × height to get cubic inches (or cubic centimetres).
- Divide by the divisor and round the result up to the next whole pound (or the carrier's kg step).
- Compare with the actual weight. The higher of the two is what you pay for.
Written out: DIM weight (lb) = L × W × H (in) ÷ 139 for most US parcel rates, and DIM weight (kg) = L × W × H (cm) ÷ 5,000 for most express couriers.
DIM divisors by carrier in 2026
The divisor is the number of cubic inches a carrier counts as one pound (or cubic centimetres as one kilogram). A lower divisor means a higher dimensional weight for the same box.
| Carrier | Divisor (inches → lb) | Divisor (cm → kg) | Notes |
|---|---|---|---|
| UPS | 139 daily rates, 166 retail rates | 5,000 | Each side rounded up to the next inch |
| FedEx | 139 | 5,000 | Rounds every fraction of an inch up since 18 August 2025 |
| USPS | 139 (was 166 until 12 July 2026) | n/a | Only on parcels over 1 cubic foot (1,728 cubic inches) |
| DHL Express | n/a | 5,000 | DHL calls it volumetric weight |
| Air freight (IATA) | ≈166 | 6,000 | Standard for air cargo, not parcels |
Negotiated contracts often use a different divisor, so check your carrier agreement before you build a shipping cost model. A move from 166 to 139 raises the DIM weight of the same box by about 19%.
Worked example in inches
A store ships a 6 lb order in an 18 × 14 × 10 inch box.
- Cubic size: 18 × 14 × 10 = 2,520 cubic inches.
- UPS daily rates, FedEx or USPS: 2,520 ÷ 139 = 18.13, rounded up to 19 lb.
- UPS retail rates: 2,520 ÷ 166 = 15.18, rounded up to 16 lb.
- Billable weight: 19 lb, more than three times what the order actually weighs.
Before July 2026 the same box shipped by USPS billed at 16 lb. After the change it bills at 19 lb, the same as UPS and FedEx.
Worked example in centimetres and kilograms
A 45 × 35 × 25 cm box holds a 4 kg order sent by an express courier.
- Cubic size: 45 × 35 × 25 = 39,375 cm³.
- Volumetric weight: 39,375 ÷ 5,000 = 7.88 kg.
- Most couriers round up to the next 0.5 kg, so the parcel bills at 8 kg, double its actual weight.
A quick rule: at a divisor of 5,000, one cubic metre counts as 200 kg. At 139, anything lighter than about 12.4 lb per cubic foot (1,728 ÷ 139) is billed on its size, not its weight. Pillows, lampshades and boxed apparel fall below that line; books and tools usually do not.
Dimensional weight vs actual weight
- Actual weight
- What the parcel weighs on a scale, rounded up to the next pound or 0.5 kg.
- Dimensional weight
- A weight calculated from the parcel's size with the carrier's divisor.
- Billable weight
- The higher of the two. This is the number your rate is looked up on.
If your product is dense and your box fits it tightly, actual weight usually wins and DIM weight never shows up on your invoice. If you ship light, bulky items, DIM weight sets your price almost every time.
Volumetric weight for air and sea freight
Freight forwarders use the same logic with different numbers. Air cargo normally uses 6,000 cm³ per kg (about 167 kg per cubic metre). Sea freight LCL is priced per "weight or measure", where one cubic metre is treated as 1,000 kg. Road freight ratios vary by country and carrier, so ask for the conversion in writing before you compare quotes.
How to reduce dimensional weight charges
- Use the smallest box that fits. Moving the 6 lb order above into a 16 × 12 × 10 inch box drops the billable weight from 19 lb to 14 lb on every shipment.
- Stock more box sizes. Three or four well-chosen sizes usually cover most orders with little empty space.
- Switch to poly mailers for soft goods. A flexible mailer is measured at its packed size, which is often far smaller than a carton.
- Stay under 1 cubic foot with USPS where you can. Below 1,728 cubic inches USPS charges on actual weight only.
- Measure before the carrier does. Keep a record of packed dimensions so you can dispute adjustments that appear on later invoices.
- Price shipping into the product. If DIM weight cannot be avoided, build the real cost into your price. Our guide on how to price a product for profit shows how.
Shipping is often the line that quietly erodes margin. Once you know your billable weight, run the order through the Profit Margin Calculator to see what is really left.
FAQ
What is the formula for dimensional weight?
Length × width × height ÷ divisor. Use 139 for inches and pounds at UPS daily rates, FedEx and USPS, or 5,000 for centimetres and kilograms. Round each side up first, then bill the higher of DIM weight and actual weight.
What is the USPS dimensional weight divisor in 2026?
139, since 12 July 2026. Before that USPS used 166. USPS only applies dimensional weight to parcels larger than one cubic foot.
Is volumetric weight the same as dimensional weight?
Yes. Volumetric weight is the term used by DHL and most couriers outside the US; dimensional or DIM weight is the US term. Both are size ÷ divisor.
Does dimensional weight apply to small parcels?
At UPS and FedEx it can apply to any parcel. At USPS it only applies above 1,728 cubic inches. In practice small, dense parcels nearly always bill on actual weight.