How to use the dimensional weight calculator
- Choose inches or centimeters and enter the length, width and height of one packed box.
- Enter the actual weight of one package in pounds or kilograms, and how many identical packages you are shipping.
- Pick an example divisor or enter your own. The divisor is cubic inches per pound and comes from your carrier, so confirm it with them.
- Read the dimensional weight, the actual weight and which one applies. Turn on rounding to bill in whole pounds if your carrier does.
Formula
Volume = length x width x height (in cubic inches)
Dimensional weight = volume / divisor
Billable weight = the larger of dimensional weight and actual weight
Centimeters are divided by 2.54 and kilograms are multiplied by 2.2046226218 before the calculation
If rounding is on, the billable weight is rounded up to the next whole pound. The total for several packages is the billable weight of one package times the count.
Worked example
A box that measures 20 x 16 x 12 inches has a volume of 3,840 cubic inches. With an example divisor of 139, the dimensional weight is 3,840 / 139 = 27.63 lb.
The box actually weighs 18 lb, so dimensional weight is the larger number and it applies. Rounded up to a whole pound, the billable weight is 28 lb, and three identical boxes would be billed at 84 lb.
Why carriers use dimensional weight
A large, light box takes up as much room on a truck or plane as a heavy one. Many carriers therefore compare the real weight with a weight worked out from the size, and bill the larger of the two. Packing a product in a smaller box can lower the billable weight even though the product itself does not change.
The divisor is your carrier's rule
The divisor turns volume into weight, and a smaller divisor gives a higher dimensional weight. Carriers and services set their own divisors and change them from time to time, so this page does not state one as fact. The three choices in the list are examples to try out. Use the divisor your carrier publishes, or enter it in the custom box.
Carriers can also round each dimension, apply minimum charges or add surcharges for large packages. None of that is modeled here. To convert a size or weight on its own, use the unit converter, and to find volumes of other shapes, try the volume calculator.
Comparing packaging options
Run the same product in two boxes and compare the billable weight of each. If the dimensional weight is far above the actual weight, a tighter box saves more than a lighter one. If the actual weight is higher, trimming packing space will not change the bill.
Assumptions and limits
- The divisor is in cubic inches per pound. The listed values are examples only and are not any carrier's rule. Check your carrier for the divisor that applies.
- Dimensions are used exactly as entered, with no rounding of each side. Your carrier may round each side up.
- Metric inputs are converted with 2.54 centimeters per inch and 2.2046226218 pounds per kilogram.
- Surcharges, minimum charges, zones and fuel costs are not included.
Frequently asked questions
Which weight does a carrier bill?
The greater of the actual weight and the dimensional weight. The calculator shows both and says which one applies, so you can see how close they are.
What happens when the two weights are equal?
The result says both are equal and uses that value as the billable weight.
Why does a smaller divisor raise the cost?
Dividing the volume by a smaller number gives a larger weight. A divisor of 139 gives a higher dimensional weight than 166 for the same box.
Can I enter centimeters and kilograms?
Yes. The size is converted to inches and the weight to pounds for the calculation, and results are shown in the weight unit you picked, with the billable pounds listed as well.