Importing
Dimensional weight calculator
Which weight your carrier bills on, and the box size at which that changes.
Carriers sell space, not mass. Past a certain density they stop charging for what a parcel weighs and start charging for the room it takes up. The useful question is not what your dimensional weight is — that is two lines of arithmetic — but how much smaller the box would have to be before it stopped mattering. This works out both.
Not ready to publish — placeholder data
Every carrier’s dimensional divisor is currently a placeholder set to zero. The figures below are not real. This page is noindex and out of the sitemap until each divisor has been read from the carrier’s published rate guide and dated.
4 carriers still to verify.
The parcel
Freight is only part of what a unit costs to land.
Landed cost calculatorHow the maths works
Dimensional weight is volume ÷ divisor. The divisor is published by the carrier and is the whole game: a larger divisor turns the same box into fewer billable pounds. Divisors differ by carrier, by unit system, and often between domestic and international service on the same carrier.
Rounding happens in a specific order. Each dimension is rounded first, then multiplied, then the resulting weight is rounded up. Computing the exact volume and rounding once at the end gives a lower figure than the carrier will bill, which is why the order is modelled per carrier rather than applied uniformly.
Billable weight is the greater of the two. A tie is treated as billing on actual weight, because there is no surcharge left to apply.
The break-even is actual weight × divisor. Below that volume the real weight is the larger figure and gets billed. Because volume falls with the cube of length, the linear reduction needed to reach it is the cube root of the volume ratio — which is why a box only needs to come down a little on each side to move a long way in volume.
The divisors behind this page
These are placeholders, not real divisors. This page is not indexed and is not in the sitemap until each carrier’s divisor has been read from its published rate guide and dated.
| Carrier | in³/lb | cm³/kg | Rounding | Source | Verified |
|---|---|---|---|---|---|
UPS | TODO | TODO | dims nearest, weight up | UPS published rate guide | — |
FedEx | TODO | TODO | dims nearest, weight up | FedEx Service Guide | — |
DHL Express | TODO | TODO | dims nearest, weight up | DHL Express rate and service guide | — |
USPS USPS applies dimensional weight only to some services and only above a cubic-foot threshold — verify which, and whether it applies at all to the service you use. | TODO | TODO | dims none, weight up | USPS Domestic Mail Manual | — |
Common questions
What is dimensional weight, in plain terms?
It is volume priced as if it were mass. A carrier sells space, not weight — a box of pillows takes the same room on an aircraft as a box of bolts. So beyond a certain density it charges for the room instead. Dimensional weight is that room converted into pounds or kilograms so the two figures can be compared, and you are billed on whichever is larger.
How is it calculated?
Length times width times height, divided by a number the carrier publishes called the dimensional divisor. A larger divisor is better for you, because it converts the same volume into fewer billable pounds. Divisors differ by carrier, by unit system, and frequently between domestic and international service on the same carrier.
Does rounding really change anything?
Often by a whole billable pound, which is why this page models it per carrier. Carriers round each dimension before multiplying them, then round the resulting weight up afterwards. Doing it in the other order — computing the exact volume and rounding once at the end — produces a different and lower answer than the carrier will actually charge you.
Which weight will I actually be charged on?
The greater of the actual weight and the dimensional weight. That is what billable weight means. If the two are equal there is no surcharge to apply, so it amounts to being billed on the real weight.
How much smaller does my box need to be?
Less than most people expect, because volume falls with the cube of length. Taking 10% off every side removes roughly 27% of the volume. This page computes the exact break-even size for the weight you entered and expresses it three ways: the volume, the equivalent cube, and the percentage each side would have to come down by.
Does dimensional weight apply to every service?
No, and that is a common source of surprise bills. Some services apply it only above a size threshold, some postal services apply it to certain classes only, and the divisor can differ between a domestic and an international movement on the same carrier. The service each divisor on this page applies to is recorded alongside it.
Related calculators
What this is not
This is a calculator, not a quote. Carriers apply dimensional weight differently across services, and a divisor that applies to one service on one lane may not apply to yours; surcharges, minimums and negotiated rates all sit on top of the billable weight shown here. The figures are estimates produced from dimensions you entered and from divisors that are linked and dated above. Check your own rate agreement before relying on them.