Shipping Costs · 6 min read
Volumetric vs Actual Weight: Why Your Shipping Is Priced That Way
A box of pillows weighs almost nothing but takes up a lot of space — and you will still pay a lot to ship it. That is because carriers charge by the greater of two numbers: actual weight and volumetric (dimensional) weight. Once you understand how the calculation works, you can pack smarter and lower your cost. Here is the plain-English explanation.
What is volumetric weight?
Volumetric weight is a number that represents how much space your shipment takes up, converted into a weight. Carriers use it because space in a plane or container is limited — a big, light box uses up room they could have sold to someone else, so they price by space when space is the limiting factor.
How the calculation works
For air freight, a common formula is length × width × height (in centimetres) divided by a factor such as 5000 or 6000. For example, a box that is 50 × 40 × 30 cm has a volume of 60,000 cubic cm; divided by 5000 that is 12 kg of volumetric weight. If the box actually weighs 8 kg, you are charged for 12 kg — the greater of the two.
For sea freight, large shipments are often priced by volume directly in cubic metres (CBM), where one CBM is a box one metre on each side.
Chargeable weight: the number you actually pay
The chargeable weight is simply the higher of actual weight and volumetric weight. Dense, heavy items (a box of canned food) are usually charged by actual weight. Light, bulky items (bedding, foam, lampshades) are usually charged by volumetric weight. Knowing which side your shipment falls on tells you how to save.
How to lower your chargeable weight
A few simple habits can meaningfully cut your bill.
- Use the smallest box that safely fits your items
- Fill empty space so you can use a tighter box, not a bigger one
- Compress soft goods (vacuum bags for bedding and clothes)
- Disassemble bulky items where safe to flatten them
- Combine small boxes into one well-packed box or barrel
Frequently asked questions
Why am I charged more than my box weighs?
Because the box is bulky relative to its weight, so its volumetric weight is higher than its actual weight, and you pay the greater of the two.
What is CBM in shipping?
CBM means cubic metre — the volume of a box one metre wide, long, and tall. Large sea shipments are often priced per CBM.
Does packing tighter really save money?
Yes. For light, bulky goods, using a smaller box or compressing contents directly lowers volumetric weight and your cost.
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