Parcel Volumetric Weight Calculator
Couriers do not charge by weight. They charge by the greater of the weight and the volumetric weight — the box's volume divided by a number the courier picks — which is why the same box costs different amounts with different carriers. A pillow is the classic case: light, enormous, and charged as though it were five kilograms.
What this generator does
Sorts the sides longest to shortest, multiplies them for the volume, divides by the courier's divisor for the volumetric weight, and compares it against the scales.
How to use this tool
- Measure the outside of the box, in any order.
- Weigh it packed, as it will be sent.
- Choose a courier, or the divisor yours uses.
- Read the chargeable weight and which way it is being charged.
Understanding the controls
- Length, width and height
- The outside of the packed box in centimetres, in any order — they are sorted before anything is measured, so the longest side is always treated as the length.
- Weight on the scales
- The parcel packed and sealed, as it will actually be handed over. Underestimating this is the other way a quote goes wrong.
- Courier
- Which divisor applies. Five thousand is the most common, six thousand is more generous, and postal services often use four thousand — the smaller the divisor, the more you pay for a big light box.
- How many parcels
- For a batch of identical parcels, to give the total chargeable weight in one go.
Common use cases
- Working out why a light parcel costs as much as a heavy one
- Comparing carriers whose divisors differ before booking
- Checking a box against the length and girth limits before packing it
- Deciding whether a smaller box would be cheaper to send
- Totalling the chargeable weight for a batch of identical parcels
How this generator works
The volume is the three sides multiplied together, and the volumetric weight is that volume divided by the courier's divisor. The check divides it back out and compares against the volume, so the divisor cannot be applied twice or not at all. Girth is where the second mistake lives: it goes round the two shorter sides, twice each, not round the biggest face — so the check confirms the sides are sorted and that the girth is built from the second and third of them. The chargeable weight is then simply the greater of the two weights, and each stated limit is compared separately so one pass does not hide another failure.
Randomness and fairness
Nothing is random. The same box and the same courier always give the same chargeable weight.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Divisors and size limits differ between couriers and change from time to time; the figures here are the commonly published ones and are worth checking.
- Some carriers round the chargeable weight up to the next half or whole kilogram, which this does not do.
- Surcharges for long, heavy or awkward items sit on top of the weight band and are not modelled.
- International services often have their own limits, lower than domestic ones.
Privacy and your data
The measurements are used only for the arithmetic in your browser and are never uploaded or stored.
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