To calculate international postage you need three things: the real weight, the dimensions and the destination. The tricky part is that the price is not always based on what the box weighs on the scale.
Real weight vs volumetric weight
Real weight is what the packed parcel weighs. Volumetric weight reflects the space it takes in the vehicle. The courier compares both and charges the higher one, called the chargeable weight.
The volumetric weight formula
Volumetric weight (kg) = length (cm) x width (cm) x height (cm) / 5000
Some carriers use 4000 or 6000 instead of 5000, so always check the divisor of the service you choose.
A worked example
- Box: 50 x 40 x 30 cm = 60,000 cubic centimetres.
- Volumetric weight: 60,000 / 5000 = 12 kg.
- Real weight on the scale: 7 kg.
- Chargeable weight: 12 kg, because it is higher.
If you could repack the same goods into a 40 x 30 x 25 cm box, volumetric weight would drop to 6 kg and the chargeable weight would become the real 7 kg.
Next steps to get the price
- Weigh and measure the packed box.
- Work out the volumetric weight.
- Take the higher figure; carriers usually round up to the next weight band.
- Look up the rate for your destination zone, or let the shipping calculator do it for you.
Tips to pay less
- Choose a box that fits the goods tightly.
- Take products out of bulky retail packaging if that is allowed.
- Combine several purchases with package consolidation.
- Compare couriers, as divisors and rates differ. See how to choose a courier.
For the full picture, read worldwide shipping costs from Spain.
