Dimensional Weight Calculator
Calculate billable weight from parcel dimensions using carrier DIM divisors for UPS, FedEx, DHL, USPS and air freight, and see how much box space is costing you.
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Carriers charge for space, not just mass
A parcel occupies a fixed volume in a vehicle regardless of what it weighs. Carriers therefore compute a dimensional weight from the box size and bill whichever is greater, the actual weight or the dimensional weight. A box of pillows weighing two kilograms can be billed as fifteen, and a shipper who quotes on actual weight alone discovers the difference on the invoice rather than at the quote.
The divisor is the whole calculation
Dimensional weight is length times width times height divided by a divisor set by the carrier and the service. In inches and pounds the common domestic divisor is 139 for UPS and FedEx retail rates, with 166 appearing on some contract rates. In centimetres and kilograms the international standard is 5000, with 6000 used for some air freight and courier services. A lower divisor means a higher dimensional weight, so a change from 166 to 139 raises the billed weight on every lightweight parcel by about twenty percent.
Where the savings are
Because volume grows with the cube of the dimensions, small reductions in box size produce disproportionate savings. Dropping a centimetre from each side of a thirty centimetre cube removes about ten percent of the volume. The calculator shows the void space you are paying to ship and the box size at which dimensional weight would stop exceeding actual weight, which is the number that tells you whether a smaller carton is worth sourcing.
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Frequently Asked Questions
Which divisor applies to my shipment?
It depends on the carrier, the service and your contract. UPS and FedEx commonly use 139 for domestic imperial rates and 5000 for metric international. Contract rates often improve on that. Check your rate card, because the divisor is negotiable and it is where a lot of shipping cost hides.
Are dimensions rounded before the calculation?
Most carriers round each dimension to the nearest whole inch or centimetre before multiplying, and round the final dimensional weight up. That rounding can push a parcel into the next weight band on its own, which is why the tool shows both rounded and exact figures.
Do I measure the box or the contents?
The outer dimensions of the packed parcel at its longest points, including any bulges. Carriers measure what goes through the scanner, so a box that bows outward when packed measures larger than the flat carton specification.
Does dimensional weight apply to every service?
Not always to small envelopes and flat rate services, and thresholds vary. Ground services historically applied it only above a certain size, though most carriers now apply it to all parcels. Check the service terms rather than assuming.
How do I reduce dimensional weight?
Use a box that fits the contents, since volume scales with the cube of the dimensions. The tool shows the void space in your current box and the size at which actual weight would take over as the billed figure.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter box dimensions and actual weight to see the dimensional weight and which one you will be billed for.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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