Because couriers bill the greater of what a parcel weighs and what its box would weigh if it were full. A big light parcel is charged as though it were heavy.
The arithmetic
Chargeable weight is the larger of:
- The actual weight on the scale, and
- Volumetric weight — length × width × height in centimetres, divided by 5000, giving kilograms.
That divisor is the one every Indian carrier uses. Then the chargeable weights of the items are added up and rounded up to the nearest 10 grams.
An example
A 200-gram scarf in a 40 × 30 × 20 cm box.
- Actual weight: 0.2 kg
- Volume: 40 × 30 × 20 = 24,000 cm³
- Volumetric weight: 24,000 ÷ 5000 = 4.8 kg
You are billed as if it were 4.8 kg — twenty-four times what it weighs. The box did that, not the scarf.
Now the same scarf in a 25 × 20 × 5 cm box: 2,500 ÷ 5000 = 0.5 kg. Still above the actual weight, but a tenth of the bill.
What this means for you as a buyer
Big light things cost more to post than they look like they should. Cushion covers, lampshades, boxed sets, anything with air in it.
Check the delivery figure against your PIN code before you bid, so the total is not a surprise inside a thirty-minute payment window. How do I know the total before I bid?
And if the figure looks wildly out of line with the item, say so — a seller who has mis-entered a box size is overcharging you by accident and would usually rather know.
What it means for you as a seller
Use the smallest box the item is safe in. Not the smallest you have — the smallest it is safe in. Those are different and the second is the answer.
Fill in all three box dimensions in the listing. If you leave them out, the volumetric figure cannot be computed and the quote is based on weight alone — which sounds cheaper and ends with the courier correcting it afterwards, against your balance. How to pack an order
The app shows you the working rather than just the total, precisely so you can see whether the box or the scale decided it.
Where it shows up
As chargeable {weight} on the delivery quote, and as a courier correction on your statement if the declared figure was wrong. That’s not what it weighed is the route for disputing one — and it works far better with a photograph of the packed parcel on a scale. There is a deduction I do not recognise
More: why is delivery costing so much, how delivery is charged, how to set delivery prices.