Volumetric weight

A carrier sells space in a van as much as it sells weight, so every parcel is billed on the larger of two figures: its weight on the scale, or the weight it would have if its volume were filled to a standard density. That second figure is the volumetric weight, and for light products in roomy boxes it is the one on the invoice.

The calculation

Multiply length, width and height in centimetres and divide by the carrier's divisor. For road parcels in Europe the common divisor is 5,000, so one kilogram is charged for every 5,000 cubic centimetres. Some services use 4,000, which is stricter, and some economy services use 6,000, which is kinder. Air freight uses 6,000 under the airline rule. The billable weight is the higher of the actual and the volumetric figure, usually rounded up to the next half or whole kilogram, with each dimension rounded up to the next whole centimetre before the sum is done.

Take a pair of trainers that weighs 1.2 kg and travels in a box of 40 × 30 × 30 cm. The volume is 36,000 cubic centimetres; divided by 5,000 that is 7.2 kg. The parcel is billed as 7.2 kg, six times its actual weight. Put the same trainers in a 34 × 22 × 13 cm box and the volumetric weight falls to 1.9 kg, so the bill falls with it.

A light product in a big box is billed as a heavy one. The box decides the price.

Length plus girth

Beyond volume, most networks set limits on size. Girth is the distance around the parcel at its widest, twice the width plus twice the height, and length plus girth is the longest side added to that. Past a threshold, a parcel stops being standard: it attracts an additional handling or large-parcel charge, and past a second threshold the network refuses it. Typical triggers are a longest side over one metre, a second side over about 75 centimetres, or a weight over the network's standard band. The exact figures sit in each carrier's service guide and in the terms you accepted, and they differ between networks, which is one reason a bulky product can belong on one carrier and not on another.

Depot re-rates

The carrier measures parcels at the depot. When its measurement differs from the figures declared on the label, it bills its own figure and adds a correction line. The usual causes are dimensions taken from the product rather than the packed box, a box swapped at the bench for a bigger one because the right size ran out, and a padded mailer that bulges once it is filled. Each of those turns into a line on the invoice weeks after the parcel left.

Accurate dimensions

Every product record in your account holds its weight in grams and its dimensions in millimetres, set once, and the label is printed from that record rather than from a packer's estimate. The rule that picks a carrier at label time sees the parcel as the carrier will see it, so a bulky item can be routed to the service that charges least for its size. The invoice audit reads every carrier line against the parcel as shipped and flags each dimensional re-rate with the declared and the billed figures side by side, so your team can decide whether to dispute it. On our rates, the billed weight and any correction appear at the carrier's price with zero markup, on their own lines.

Packing habits

Choose box sizes to fit the products you ship: two or three sizes that fit your best sellers closely save more than one box that fits everything. Record the packed dimensions, not the catalogue ones, on every product that ships in its own box. And check the volumetric weight of your ten most-shipped products once; where it beats the actual weight by a wide margin, a smaller box or a mailer usually pays for itself.