Shipping
Dimensional weight explained: why a light box can cost more to ship
Couriers bill the greater of actual and dimensional weight. See the formula, a worked example, why divisors differ, and how to cut the cost of bulky parcels.
· 2 min read
A pillow weighs almost nothing, yet shipping it can cost more than shipping a small, heavy tool. The reason is dimensional weight, also called volumetric weight. Couriers need to charge for the space a parcel takes in a vehicle or aircraft, not only for its weight.
How it works
Dimensional weight = Length x Width x Height / Divisor
Chargeable weight = the greater of actual weight and dimensional weight
You measure the packed parcel, not the product. The divisor is set by the carrier. Different carriers, services and countries use different divisors, so always check the figure for the service you use. Metric rates are commonly quoted with divisors such as 5000 or 6000 (centimetres and kilograms), and imperial rates with figures such as 139 or 166 (inches and pounds), but treat these as examples to verify, not facts about your carrier.
A worked example
A parcel measures 30 x 20 x 10 cm and weighs 1 kg. The carrier uses a divisor of 5000 and charges 400 per kg, and packaging costs 50.
| Step | Calculation | Result |
|---|---|---|
| Volume | 30 x 20 x 10 | 6,000 cm3 |
| Dimensional weight | 6,000 / 5,000 | 1.2 kg |
| Chargeable weight | greater of 1 kg and 1.2 kg | 1.2 kg |
| Shipping cost | 1.2 x 400 + 50 | 530 |
You pay for 1.2 kg even though the parcel weighs 1 kg. If the same box were packed 5 cm shorter, the volume and the bill would fall.
How to lower the bill
- Use the smallest box or mailer that protects the product. Empty space is billed like product.
- Switch to soft poly mailers for items that do not need a rigid box.
- Compare services. A carrier with a higher divisor charges less for light, bulky parcels.
- Fold, compress or flat-pack products where it is safe, and re-measure after packing.
Enter your parcel and divisor in the Shipping Cost Calculator to see the chargeable weight, then build that cost into your price with the Product Pricing Calculator.
This guide is general information with simplified examples. It is not financial, tax or legal advice. Your real fees, costs and results will differ, so check them against your own marketplace and carrier statements.