Volumetric weight is the weight a carrier assigns to your parcel based on the space it takes up. Multiply length, width and height in centimetres, then divide by 6000 for air freight or 5000 for express couriers. You are billed on the greater of that figure and the actual weight, called chargeable weight.
What is volumetric weight and why do carriers use it?
Volumetric weight is a weight figure worked out from the size of your package, not from the scale. Carriers use it because space on a plane, truck or ship is limited, and a big, light box takes up as much room as a heavy one.
The carrier compares the volumetric weight with the actual (gross) weight and bills the higher number. That higher number is the chargeable weight. A box of pillows that weighs 5 kg on the scale but fills a large carton is billed for the size of the carton, not its weight.
How do you calculate volumetric weight?
You can also use our Volumetric Weight Calculation tool to calculate your shipment’s volumetric weight and estimate the shipping cost based on its dimensions and actual weight.
Measure the packed box, multiply the three sides, then divide by the carrier’s divisor. Work through these steps.
- Measure the final packed box in centimetres at its longest points, including any bulges. Length is the longest side.
- Multiply length by width by height to get cubic centimetres.
- Divide by the divisor for your mode (see the table below).
- Weigh the fully packed box on a scale.
- Compare the two numbers. The higher one is your chargeable weight.
- Round up if your carrier does. Many round each dimension up to the next whole centimetre and the final weight up to the next 0.5 kg or 1 kg.
Here is a worked example for air freight. A box measures 60 x 40 x 40 cm, which is 96,000 cubic centimetres. Divided by 6000, that is 16 kg. The box weighs 9 kg on the scale, so you are billed for 16 kg. An express courier that divides by 5000 gets 19.2 kg, which a carrier that rounds up to the next 0.5 kg bills as 19.5 kg.
If you measure in inches, the same method works with 166 for air freight or 139 for express couriers, and the answer comes out in pounds. Don’t mix units.
Which divisor should you use for each mode?
It depends on the mode and the carrier, and the carrier’s rate card has the final say. The divisor is the number you divide the cubic volume by. These are the common values.
| Mode | Common divisor | 1 CBM counts as | How you are billed |
|---|---|---|---|
| Air freight | 6000 (IATA standard) | About 167 kg | Greater of actual and volumetric weight |
| Express courier | 5000 | 200 kg | Greater of actual and volumetric weight |
| Road freight (LTL) | 3000 | About 333 kg | Greater of actual and volumetric weight |
| Sea freight (LCL) | 1,000 kg per CBM | 1,000 kg | Greater of CBM or tonnes |
| Sea freight (FCL) | None | Not applicable | Flat price per container |
A smaller divisor gives a bigger volumetric weight, which is one reason express services can cost more for the same box. Road carriers vary: some use 250 or 300 kg per CBM instead of 333. Australian courier guidance also lists 250 kg per CBM for domestic express freight and 333 for general freight. Always confirm the figure in your carrier’s terms before you compare quotes.
How does volumetric weight work in sea freight?
LCL sea freight uses the weight or measure (W/M) rule: you pay on whichever is greater, the volume in cubic metres or the weight in tonnes, with 1 CBM treated as 1,000 kg. There is no divisor in the formula.
Take a pallet measuring 1.2 x 1.0 x 1.0 m. That is 1.2 CBM. At 300 kg (0.3 tonnes), volume is greater, so you pay for 1.2 units. A dense crate of 0.5 CBM weighing 800 kg (0.8 tonnes) is billed on weight, so you pay for 0.8 units. FCL is priced per container, so volumetric weight doesn’t change the freight price.
If you need help working out the volume, see our guide on how to calculate CBM.
How does volumetric weight change what you pay?
It can raise your bill without any change in what you ship. This example uses an illustrative rate of 6 per kg, not Postkodes rates.
The 60 x 40 x 40 cm box weighing 9 kg is billed on 16 kg, which is 96. On actual weight it would be 54, so the box size adds 42. Now repack the goods into a 50 x 35 x 30 cm carton. That is 52,500 cubic centimetres, which divided by 6000 is 8.75 kg. The actual weight of 9 kg is now the higher figure, so you are billed on 9 kg, which is 54.
The rate per kilogram didn’t change. The box did. This only works if the goods still fit with enough protection.
How can you reduce volumetric weight?
- Use the smallest box that still protects the goods.
- Remove empty space and extra void fill.
- Use padded mailers or flat packing for soft goods, and vacuum packing where it is suitable.
- Check the size after sealing, since a bulging box can add centimetres on every side.
- Ask your carrier for its divisor and rounding rule before you choose a box size.
What mistakes lead to a higher bill?
- Measuring the product instead of the packed box.
- Leaving out bulges or protruding parts.
- Using the wrong divisor for the service.
- Mixing units, such as centimetres with an inch divisor.
- Averaging pieces. Some carriers calculate each piece separately, so a dense small carton doesn’t offset a light, bulky one.
- Ignoring rounding, which can nudge a box into the next weight step.
Will the carrier check your measurements?
Yes, usually. Parcels and freight are commonly re-weighed and re-measured at the terminal, and if the measured size gives a higher volumetric weight than you declared, billing follows the measured figure.
Measure the sealed package at its outer points. Take a photo of it beside a tape measure and the scale reading, and use the same numbers when you request a quote.
How do you get a quote with the right weight?
Enter the actual weight and the packed dimensions, and ask the quote to state the chargeable weight. Postkodes’ Quick Quote page asks for weight, quantity and dimensions in centimetres, so use your measured, packed figures.
Air shipments are where volumetric weight matters most, so if you’re comparing options, take a look at Postkodes’ air freight services.
Frequently asked questions
What is the volumetric weight formula?
For air freight, length times width times height in centimetres divided by 6000 gives kilograms. Express couriers usually divide by 5000. The carrier compares the result with actual weight and bills the higher number.
Why is my parcel billed for more than it weighs?
Because it takes up more space than its weight suggests. Light, bulky items like pillows or empty cartons hit the volumetric figure first, so the carrier bills that instead of the scale weight. Smaller packaging usually lowers it.
Does sea freight use volumetric weight?
LCL uses a similar rule: you pay on the greater of cubic metres or tonnes, with 1 CBM treated as 1,000 kg. FCL is a flat price per container, so volumetric weight does not apply to the price.
Which divisor do road freight carriers use?
It varies. Many use 3000, which equals about 333 kg per CBM, while some use 250 or 300 kg per CBM. Always check the carrier’s terms before you compare quotes, because the same pallet can be billed very differently.
Do carriers re-measure packages?
Yes. Parcels are often re-measured at the terminal, and if the verified dimensions give a higher volumetric weight than you declared, billing follows the measured figure. Measure the sealed package at its outer points and keep photos.
Do I round the measurements?
Many carriers round each dimension up to the next whole centimetre and the final weight up to the next 0.5 kg or 1 kg. Rounding rules differ, so use your carrier’s rule, and round up when unsure.
What should you do next?
Measure the packed box, work out both the volumetric and the actual weight, and compare them before you book. If the volumetric figure is higher, try a smaller box before you pay for the extra weight.
When you’re ready for a price, request an estimate through the Quick Quote page and enter your packed dimensions and weight.
