You ship a cushion weighing half a kilo and get billed for three. That is not a carrier error — it is volumetric weight.
How it is calculated
The carrier takes the parcel's volume (length × width × height) and divides it by a fixed factor. The result is the volumetric weight. It is compared with the actual weight, and you are billed on whichever is greater.
Why it matters
Because most quiet shipping losses come from here. You price shipping on product weight, then discover at month-end that you paid double what you collected from customers.
How to reduce it
- Use the smallest box that genuinely protects the product — not the box you happen to have.
- Remove internal void: excess filler adds volume for nothing.
- For soft goods, use mailers instead of boxes.
- Standardise packaging into three sizes whose cost you know precisely.
Enter dimensions on every product
The length, width and height fields are not cosmetic — without them the store cannot estimate shipping accurately, and you absorb the difference.
Test with a real parcel
Take your three best sellers, pack them the way you actually pack them, and calculate volumetric weight. The gap between that figure and what you charge is your profit or loss on every order.