About the Dimensional Weight Calculator
This dimensional weight calculator shows the weight a carrier will actually charge for a parcel. Couriers price by space as well as mass, so a large light box is billed at its dimensional (volumetric) weight — length × width × height divided by a DIM divisor — whenever that is higher than what it weighs on the scale. Enter the box dimensions and actual weight, choose the carrier divisor, and get the DIM weight, the billable weight and which of the two applies.
It is useful for e-commerce sellers choosing box sizes, warehouse teams quoting shipping, and anyone comparing UPS, FedEx, USPS, DHL or other express couriers. Common divisors are included: 139 in³/lb for UPS and FedEx daily rates, 139 in³/lb for USPS (since July 12, 2026, replacing 166, and still applied only to parcels over one cubic foot), 5000 cm³/kg for most international express services and 6000 cm³/kg for air freight and some carriers.
Imperial results follow the current US carrier rules for rectangular boxes: any fraction of an inch is rounded up to the next whole inch (UPS and FedEx since August 2025, USPS since July 2026), and weights round up to the next pound. The USPS 166 divisor and 0.785 factor for non-rectangular parcels are not modelled. Metric dimensions are rounded up to the next whole centimetre and the billable weight up to the next 0.5 kg (FedEx rounds metric DIM weight to the next whole kg). Check your own contract, as negotiated divisors differ.
How to use the dimensional weight calculator
- 1Choose inches and pounds or centimetres and kilograms.
- 2Measure the box at its longest points and enter length, width and height.
- 3Enter the actual weight from your scale.
- 4Pick the carrier divisor that matches your service.
- 5Read the billable weight and whether size or weight is driving the price.
Formula and method
Dimensional weight is the package volume divided by the carrier’s DIM divisor. With inches and pounds, UPS and FedEx daily rates use 139, and USPS also uses 139 from July 12, 2026 (previously 166), but only for parcels over 1,728 in³. With centimetres and kilograms, international express carriers typically use 5000 and air freight 6000. A smaller divisor produces a higher dimensional weight.
The carrier bills whichever is greater: dimensional weight or actual weight. For imperial divisors this calculator rounds any fractional dimension up to the next whole inch (so 11.1 in counts as 12 in) and rounds both weights up to the next whole pound, as UPS, FedEx and USPS now do. For metric divisors each dimension is rounded up to the next whole centimetre and the billable weight up to the next 0.5 kg; some carriers, including FedEx, round to the next whole kilogram instead. Your negotiated contract may use different rules.
- L, W, H
- Package length, width and height (longest side is length)
- Divisor
- Carrier DIM factor — 139 in³/lb, or 5000 or 6000 cm³/kg
Worked examples
18 × 12 × 10 in box weighing 15 lb (UPS/FedEx)
18 × 12 × 10 = 2,160 in³. Divided by 139 that is 15.54, rounded up to 16 lb. The actual 15 lb is lighter, so the carrier bills 16 lb — the dimensional weight.
Metric express shipment: 50 × 40 × 30 cm, 8 kg
50 × 40 × 30 = 60,000 cm³. Divided by 5,000 the volumetric weight is 12 kg, which beats the 8 kg actual weight, so the courier bills 12 kg (about 26.5 lb).
Large USPS box: 20 × 14 × 12 in, 9 lb
20 × 14 × 12 = 3,360 in³, over the 1,728 in³ USPS threshold. 3,360 ÷ 139 = 24.17, rounded up to 25 lb, which is billed instead of the 9 lb actual weight. Under the old 166 divisor it would have been 21 lb.
Fractional dimensions: 11.1 × 8.2 × 6.5 in, 2 lb (UPS/FedEx)
Each fraction rounds up to the next inch, so the box counts as 12 × 9 × 7 = 756 in³. 756 ÷ 139 = 5.44, rounded up to 6 lb, which beats the 2 lb actual weight.
Small dense USPS parcel: 10 × 8 × 6 in, 3.2 lb
At 480 in³ the box is under one cubic foot, so USPS does not apply dimensional weight. The 3.2 lb actual weight rounds up to 4 lb billable.
Frequently asked questions
How do you calculate dimensional weight?+
Multiply length × width × height of the package and divide by the carrier’s DIM divisor. In inches and pounds UPS and FedEx use 139, so a 20 × 16 × 12 in box is 3,840 ÷ 139 = 27.6, billed as 28 lb.
What is the DIM divisor for UPS, FedEx and USPS?+
UPS and FedEx use 139 cubic inches per pound for daily (account) rates. USPS moved from 166 to 139 on July 12, 2026 for Priority Mail, Ground Advantage and Parcel Select, but still applies it only to parcels larger than one cubic foot. Negotiated contracts can use higher divisors, which lower dimensional weight.
Do carriers round package dimensions up?+
Yes. FedEx and UPS (from August 18, 2025) and USPS (from July 12, 2026) round any fraction of an inch up to the next whole inch before multiplying, so an 11.1 in side is measured as 12 in. The dimensional weight is then rounded up to the next whole pound.
What is billable weight?+
Billable (chargeable) weight is the weight a carrier uses to price a shipment: the greater of the actual scale weight and the dimensional weight. Light but bulky parcels are billed on dimensional weight.
What is the difference between 5000 and 6000 volumetric divisors?+
Both are metric divisors in cm³ per kg. 5000 is common for international express couriers and gives a higher volumetric weight; 6000 (the IATA air cargo standard) gives a lower one. Always check which your carrier uses.
How can I reduce dimensional weight charges?+
Use the smallest box that protects the product, avoid excess void fill, consider poly mailers for soft goods and negotiate a higher DIM divisor if you ship in volume. Cutting just one inch off each side can drop several billable pounds.