Couriers fill trucks and aircraft by space as much as by weight, so a big, light box costs them as much as a small, heavy one. Dimensional weight converts a parcel’s volume into a notional weight; you pay for whichever is greater, the scale weight or the DIM weight.
The divisor sets the conversion. In the United States UPS (daily rates) and FedEx use 139 cubic inches per pound, UPS retail rates use 166, and since 12 July 2026 USPS also uses 139 for Priority Mail, Priority Mail Express, Ground Advantage and Parcel Select parcels larger than one cubic foot (1,728 in³). Internationally and in metric countries, DHL Express, FedEx and UPS use 5,000 cm³ per kg; some economy and postal services use 6,000. Since 18 August 2025 UPS and FedEx round every fractional inch up to the next whole inch before multiplying, and USPS adopted the same rounding in July 2026.
Enter the box size and actual weight and choose a divisor. The calculator applies the rounding (whole inches and pounds for the imperial divisors, whole centimetres and half kilograms for the metric ones), and lists the DIM and billable weight for each major carrier so you can compare. Shrinking a box by even an inch on each side often saves a whole billing tier.
How to use the Dimensional Weight Calculator
- Length
- Width
- Height
- Actual weight
- Carrier divisor
- Carrier rounding
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Dimensions are converted to inches or centimetres, rounded up if rounding is on, multiplied and divided by the divisor. Imperial results are rounded up to the next pound, metric ones to the next 0.5 kg. The billable weight is the greater of the DIM weight and the (rounded) actual weight.
Worked example
A 50 × 40 × 30 cm box weighing 6 kg. Metric (÷ 5,000): 60,000 cm³ ÷ 5,000 = 12 kg, so you are billed for 12 kg. In inches the box is 19.7 × 15.7 × 11.8, rounded up to 20 × 16 × 12 = 3,840 in³; ÷ 139 = 27.6 → 28 lb (12.70 kg) for UPS daily and FedEx, ÷ 166 = 23.1 → 24 lb for UPS retail. The actual 6 kg (13.2 → 14 lb) is lower, so DIM weight applies everywhere.
Divisors by carrier (2026)
| Carrier / service | Divisor |
|---|---|
| UPS daily rates | 139 in³/lb |
| UPS retail rates | 166 in³/lb |
| FedEx (US) | 139 in³/lb |
| USPS (from 12 July 2026, > 1 ft³) | 139 in³/lb |
| DHL Express, metric UPS/FedEx | 5,000 cm³/kg |
Tips
- Measure the longest points of the package, including bulges.
- Check your carrier’s current divisor and rounding rules.
- Every field has a unit menu: cm, inches, kg and lb all work.
- Everything is calculated in your browser.
Common mistakes to avoid
- Using the wrong dimensional divisor for the carrier or service.
- Forgetting pallet height and overhang limits.
- Rounding dimensions down instead of up.
Inputs explained
| Field | What to enter |
|---|---|
| Length | Units: cm, in, mm, m |
| Width | Units: cm, in, mm, m |
| Height | Units: cm, in, mm, m |
| Actual weight | Units: kg, lb, t, g |
| Carrier divisor | Choose one: 139 in³/lb: UPS daily, FedEx, USPS (from 12 July 2026), 166 in³/lb: UPS retail rates, 5,000 cm³/kg: DHL Express, FedEx/UPS metric & international, 6,000 cm³/kg: some economy and postal services … |
| Carrier rounding | Choose one: Round up as carriers do, Exact (no rounding) |
What each result means
- UPS daily / FedEx (÷ 139) = max(ceil([Li]×[Wi]×[Hi]÷139 – 1e-9), [lbr])×0.45359237
- UPS retail (÷ 166) = max(ceil([Li]×[Wi]×[Hi]÷166 – 1e-9), [lbr])×0.45359237
- DHL Express (÷ 5,000 cm³/kg) = max(ceil([Lc]×[Wc]×[Hc]÷5000×2 – 1e-9)÷2, [kgr])
- Package volume (rounded sides) = [Li]×[Wi]×[Hi]
- Package volume in litres = [Length]×[Width]×[Height]÷1000
Formula
DIM weight (lb) = L × W × H (in) ÷ 139 (or 166) · DIM weight (kg) = L × W × H (cm) ÷ 5,000 · Billable weight = max(actual, DIM) · US carriers round each side up to the next inch and the weight up to the next lb
Worked example
Inputs: Length: 50 cm; Width: 40 cm; Height: 30 cm; Actual weight: 6 kg; Carrier divisor: 5,000 cm³/kg – DHL Express, FedEx/UPS metric & international; Carrier rounding: Round up as carriers do.
Results: Dimensional weight = 12 kg; Billable weight = 12 kg; Charged on = Dimensional weight – the box is large for its weight; UPS daily / FedEx (÷ 139) = 12.7 kg; UPS retail (÷ 166) = 10.89 kg; USPS (÷ 139 above 1 ft³) = 12.7 kg; DHL Express (÷ 5,000 cm³/kg) = 12 kg; Package volume (rounded sides) = 3,840 in³; Package volume in litres = 60 L.
Key terms
- Dimensional (DIM) weight
- Weight calculated from package volume.
- Divisor
- Volume per unit of weight used by the carrier (in³/lb or cm³/kg).
- Billable weight
- Weight the shipment is charged on.
Frequently asked questions
What is the dimensional weight divisor for UPS and FedEx?
139 in³/lb for daily (account) rates; UPS retail rates use 166. Metric and international shipments use 5,000 cm³/kg.
Did USPS change its DIM divisor?
Yes, from 12 July 2026 USPS uses 139 (previously 166) for parcels over 1 cubic foot, and rounds fractional inches up.
How do I calculate dimensional weight?
Multiply length × width × height and divide by the divisor: 20 × 16 × 12 in = 3,840 in³ ÷ 139 = 27.6 → 28 lb.
Do carriers round the dimensions?
UPS and FedEx round each side up to the next whole inch (since August 2025) and the DIM weight up to the next pound.
What is billable weight?
The larger of the actual weight and the dimensional weight.
How can I reduce dimensional weight?
Use the smallest box that protects the item, avoid air space, and consider poly mailers for soft goods.
What divisor does DHL use?
5,000 cm³/kg for DHL Express (equivalent to about 139 in³/lb).