Air freight calculator

Why Two Boxes the Same Weight Can Cost Completely Different Amounts

Send a 10kg box of steel brackets and a 10kg box of pillows on the same flight, and you'll get two very different invoices. Air freight isn't charged purely on weight. It's charged on whichever is higher: the actual weight on the scale, or the volumetric weight calculated from the space the shipment takes up in the aircraft hold.

That second number catches people out constantly, especially first-time exporters quoting based on weight alone. A pallet of light, bulky stock can rack up a volumetric weight three or four times its actual weight, and the carrier will charge for the bigger figure every time.

The Volumetric Weight Formula, Step by Step

IATA's standard formula for air freight is: (Length × Width × Height in cm) ÷ 6000. Some courier networks use 5000 instead of 6000 for certain lanes, which produces a slightly higher volumetric figure, so always check which divisor your carrier or freight forwarder actually applies.

Take a carton measuring 60cm × 40cm × 35cm. Multiply those together and you get 84,000 cubic centimetres. Divide that by 6000 and you land on exactly 14kg of volumetric weight. If the actual scale weight of that carton is only 9kg, the airline charges for 14kg, not 9 — the volumetric figure wins because it's higher.

Now scale that up. Five identical cartons at 14kg volumetric each gives you 70kg total volumetric weight, against maybe 45kg of actual weight combined. That 25kg gap is pure margin loss if you've quoted your customer based on the bathroom-scale number.

Rounding Rules Most People Miss

Air freight invoices typically round chargeable weight up to the nearest 0.5kg. A calculated chargeable weight of 14.2kg gets billed as 14.5kg. It sounds trivial on one shipment, but across hundreds of cartons a year it adds up to real money, and it's why the calculator above rounds the same way your invoice will.

A Real Shipping Scenario

An online retailer in Melbourne is importing 20 cartons of lightweight homewares from a supplier in Guangzhou. Each carton is 50cm × 40cm × 30cm and weighs 8kg. Volumetric weight per carton: (50×40×30)/6000 = 10kg. Actual weight per carton: 8kg. Chargeable weight per carton: 10kg, because the volumetric figure is higher.

Across 20 cartons, that's 200kg chargeable instead of 160kg actual — a 25% jump. At a typical air freight rate of $7.50/kg out of Guangzhou, that's the difference between a $1,200 quote and a $1,500 invoice. Getting the volumetric number wrong at the quoting stage is how freight forwarders lose money on fixed-price jobs.

For anyone regularly comparing options, it's worth cross-checking against a dimensional weight reference to confirm which divisor applies to a specific carrier or freight lane, since not every operator uses the IATA default.

When Sea Freight Becomes the Better Option

If your shipment's volumetric weight is several times its actual weight — light, bulky goods like foam packaging, soft toys, or empty containers — ocean freight charged by CBM (cubic metres) often works out far cheaper than air, even with the longer transit time. The crossover point is usually somewhere around 100–150kg actual weight for low-density cargo, but it depends heavily on the specific rate card.

FAQs

What is chargeable weight in air freight?

Chargeable weight is whichever is higher between the shipment's actual weight and its volumetric weight. Carriers always bill on the larger of the two figures, never the smaller.

How do you calculate volumetric weight for air cargo?

Multiply length × width × height in centimetres, then divide by 6000 (the IATA standard divisor). The result is the volumetric weight in kilograms for that piece.

Why is air freight more expensive for bulky, light items?

Because aircraft cargo holds run out of space before they run out of weight capacity on most routes. Light, bulky shipments take up disproportionate space relative to their actual weight, so carriers charge on volume to recover that lost capacity.

Is the volumetric divisor always 6000?

No. 6000 is the IATA international standard, but some couriers and specific domestic services use 5000, which produces a higher volumetric weight for the same dimensions. Always confirm with your specific carrier.

How is chargeable weight rounded on an invoice?

Most air freight invoices round the calculated chargeable weight up to the nearest 0.5kg. A figure of 14.2kg becomes 14.5kg on the final invoice.

Should I use CBM or volumetric weight for my shipment?

Volumetric weight (in kg) is the standard for air freight. CBM (cubic metres) is the standard unit for sea freight, where pricing usually runs per cubic metre rather than per kilogram.

Does air freight pricing include customs clearance?

Usually not. The per-kg air freight rate covers transport only. Customs clearance, duties, GST, and local delivery are typically quoted separately by your freight forwarder or customs broker.

Run the dimensions through properly before you quote a customer or budget a shipment, not after. The 25% gap in the example above isn't an edge case, it's closer to the norm for anything that isn't dense, heavy cargo — and it's the single most common reason freight quotes come in under what actually lands on the invoice.