# What is the dimensional weight?

Works out a package’s dimensional (volumetric) weight from its length, width and height and the carrier’s divisor, and the billable weight: the larger of the dimensional and actual weights.

- Page: https://www.acalculator.org/logistics/dimensional-weight-calculator
- JSON spec: https://www.acalculator.org/logistics/dimensional-weight-calculator.json
- Version: faec5b98600c

## Default answer

Example with the default inputs (Divisor units in and lb, Length 12 in, Width 12 in, Height 12 in, Round each side Nearest whole, Divisor (in³ per lb) 139): The billable weight is 13 lb; the dimensional weight is 12.43.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| sys | Divisor units | Inches and pounds (a divisor in cubic inches per pound) or centimetres and kilograms (cm³ per kg). |
| l | Length | The package’s length, measured at its longest point. |
| w | Width | The package’s width, measured at its longest point. |
| h | Height | The package’s height, measured at its longest point. |
| r | Round each side | How the carrier rounds each measurement before multiplying: to the nearest whole inch or centimetre, up to the next whole one, or not at all. |
| div | Divisor (in³ per lb) | The carrier’s dimensional divisor in cubic inches per pound. |
| divm | Divisor (cm³ per kg) | The carrier’s dimensional divisor in cubic centimetres per kilogram. |
| wt | Actual weight | What the package weighs on a scale. Leave it empty to see the dimensional weight alone. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| result | Billable weight | The weight the carrier charges for: the larger of the dimensional and actual weights, each rounded up to the next whole pound or kilogram. |
| dimWeight | Dimensional weight (lb or kg) | Length × width × height ÷ divisor, before rounding up, in pounds or kilograms by the divisor units. |
| dimRounded | Dimensional weight, rounded up | The dimensional weight rounded up to the next whole pound or kilogram. |
| billable | Billable weight (lb or kg) | The larger of the rounded dimensional weight and the rounded actual weight. |
| volume | Volume (in³ or cm³) | The product of the three rounded sides, in cubic inches or cubic centimetres. |

## Method

Dimensional weight = L × W × H ÷ divisor (in³ per lb, or cm³ per kg), each side first rounded as chosen; rounded up to the next whole lb or kg. Billable weight = the larger of that and the actual weight rounded up.

## Assumptions

- Carriers set their own divisors and rounding rules, and change them. Check the carrier’s current rules for your account.
- Some services charge dimensional weight only above a size (USPS: over 1 cubic foot, 1,728 in³). The page always shows it.
- The steps are exact on the numbers as typed; only the final roundings are shown.

## Worked examples

1. sys = us, l = 0.3048, w = 0.3048, h = 0.3048, r = nearest, div = 139 gives dimWeight = 12.431655, dimRounded = 13, billable = 13, volume = 1,728, result = 13 lb. Source: FedEx, "What is dimensional weight?" (L × W × H in inches, each rounded to the nearest whole inch, ÷ 139), https://www.fedex.com/en-us/shipping/packaging/what-is-dimensional-weight.html (retrieved 2026-10-05).
2. sys = us, l = 0.3048, w = 0.3048, h = 0.3048, r = nearest, div = 166, wt = 2.267962 gives dimWeight = 10.409639, dimRounded = 11, billable = 11, result = 11 lb, by size. Source: USPS Postal Bulletin 22509 (round each measurement to the nearest whole inch, divide by 166 and round up to the next whole pound), https://about.usps.com/postal-bulletin/2018/pb22509/html/updt_002.htm (retrieved 2026-10-05).
3. sys = metric, l = 0.36, w = 0.25, h = 0.16, r = nearest, divm = 5,000 gives dimWeight = 2.88, dimRounded = 3, volume = 14,400. Source: FedEx UK, "Understand dimensional weight" (36 × 25 × 16 cm ÷ 5,000 is a DIM weight of 3 kg), https://www.fedex.com/en-gb/how-to/calculate-costs/dimensional-weight.html (retrieved 2026-10-05).
4. sys = us, l = 0.31496, w = 0.26924, h = 0.2159, r = up, div = 139, wt = 6.350293 gives volume = 1,287, dimWeight = 9.258993, dimRounded = 10, billable = 14, result = 14 lb, by weight. Source: FedEx, "What is dimensional weight?" (L × W × H in inches, each rounded to the nearest whole inch, ÷ 139), https://www.fedex.com/en-us/shipping/packaging/what-is-dimensional-weight.html (retrieved 2026-10-05).
5. sys = us, l = 0.31496, w = 0.26924, h = 0.2159, r = nearest, div = 139 gives volume = 1,188, dimRounded = 9. Source: USPS Postal Bulletin 22509 (round each measurement to the nearest whole inch, divide by 166 and round up to the next whole pound), https://about.usps.com/postal-bulletin/2018/pb22509/html/updt_002.htm (retrieved 2026-10-05) (nearest whole inch).

## FAQ

### How do I calculate dimensional weight?

Round each side of the box as the carrier says (often to the nearest whole inch), multiply length × width × height, and divide by the carrier’s divisor. Round the result up to the next whole pound. A 12-inch cube is 1,728 cubic inches; at a divisor of 139 that is 12.43, so 13 lb.

### What is the billable weight?

It is the weight the carrier charges for: the larger of the dimensional weight and the actual weight on a scale, each rounded up to the next whole pound or kilogram. A light but bulky box is billed by its size; a small heavy one by its weight.

### What divisor should I use?

Use the one your carrier and rate type state. In the US, many carriers use 139 cubic inches per pound for daily rates and 166 for retail rates; USPS uses 166. In centimetres and kilograms, 5,000 cm³ per kg is the most common. A larger divisor gives a lower dimensional weight.

### Should I round the sides up or to the nearest inch?

It depends on the carrier and changes over time. FedEx’s and USPS’s published rules round each side to the nearest whole inch; some carriers now round up to the next whole inch. Pick the rule your carrier uses in the "Round each side" box.

### Does USPS charge dimensional weight on every package?

No. USPS applies it to packages over one cubic foot (1,728 cubic inches) for the services that use it. The calculator always shows the dimensional weight, so check whether your service applies it.

### How can I lower my dimensional weight?

Use the smallest box that fits the item safely. Every inch counts three ways, because the volume multiplies all three sides; cutting a 12-inch cube to 11 inches cuts the volume by almost a quarter.

## Sources

- FedEx, "What is dimensional weight?": L × W × H in inches, each side rounded to the nearest whole inch, ÷ 139. https://www.fedex.com/en-us/shipping/packaging/what-is-dimensional-weight.html (retrieved 2026-10-05)
- FedEx UK, "Understand dimensional weight": the 5,000 cm³ per kg divisor and the 36 × 25 × 16 cm example (3 kg). https://www.fedex.com/en-gb/how-to/calculate-costs/dimensional-weight.html (retrieved 2026-10-05)
- USPS Postal Bulletin 22509: round each side to the nearest whole inch, divide by 166 and round up to the next whole pound, for parcels over 1 cubic foot. https://about.usps.com/postal-bulletin/2018/pb22509/html/updt_002.htm (retrieved 2026-10-05)