Two weights, one bill
Every air shipment is measured twice before it is priced: once on a scale, and once with a tape measure. The carrier compares the two and charges the higher figure. There is no negotiation in this step — it is the pricing rule, and it is the same one whether you book a courier envelope or a pallet.
| What is measured | How it is worked out | When it decides the bill |
|---|---|---|
| Actual (gross) weight | Weighed on a scale, packing included | Dense cargo: machinery, spares, hardware, fittings, liquids, printed matter |
| Volumetric weight | L × W × H (cm) ÷ 6,000 for each carton, then added up | Light cargo: apparel, plastics, packaging materials, furniture, most e-commerce |
| Chargeable weight | The higher of the two, calculated per shipment | Always — this is the figure the rate is multiplied by |
Why 6,000 — and why sometimes 5,000
The divisor converts volume into an equivalent weight, and it is fixed by the service you are buying rather than by the airline. Air cargo uses the IATA volumetric standard of 6,000 cm³ per kilo. Express and courier networks use 5,000 cm³ per kilo, which prices the same carton 20% heavier. That single difference is enough to make one quote look cheaper than another when the two are not the same product.
| Service | Divisor | Volume equal to 1 kg | Equivalent density |
|---|---|---|---|
| Air cargo (IATA volumetric standard) | 6,000 | 6,000 cm³ | 166.7 kg per m³ |
| Express / courier | 5,000 | 5,000 cm³ | 200 kg per m³ |
| Ocean LCL, for comparison | — | — | 1 m³ = 1,000 kg (revenue ton) |
Practical consequence: the break-even density is 166.7 kg per cubic metre. Cargo packed denser than that is billed on weight; cargo packed lighter is billed on volume. Most consumer goods sit well below the line, which is why the tape measure usually wins.
A worked example
Take one carton of 60 × 40 × 40 cm with a gross weight of 9 kg.
- Volume: 60 × 40 × 40 = 96,000 cm³
- Volumetric weight: 96,000 ÷ 6,000 = 16 kg
- Actual weight: 9 kg
- Chargeable weight per carton: 16 kg — the volumetric figure wins
Twenty cartons: 1,920,000 cm³ = 320 kg volumetric against 180 kg on the scale. The invoice is built on 320 kg. The cargo weighs 180 kg and pays for 320 — a 78% difference that has nothing to do with the quality of the packing and everything to do with the ratio of volume to weight.
Turn it around: the same 1.92 m³ loaded with 350 kg of dense goods is billed at 350 kg, because now the scale wins. The cartons did not change. Only the weight-to-space ratio did, and it decided which of the two numbers is the product you are buying.
Weight breakpoints: when heavier costs less
Air rates are not one price per kilo. Carriers publish a scale with steps, and the rate falls at each step.
| Band | What it means in practice |
|---|---|
| N (normal) | Below 45 kg. The highest rate per kilo, and every shipment also carries a minimum charge |
| +45 kg | Rate per kilo steps down |
| +100 kg | Steps down again |
| +300 kg | Steps down again |
| +500 kg | Steps down again |
| +1,000 kg | Lowest published band on most scales |
Two things follow, and both are routinely missed when a customer compares air quotes.
A shipment just below a breakpoint can be charged as if it were at it. Airlines price the option and use the cheaper of the two, so 980 kg charged as 1,000 kg at the +1,000 kg rate can come out below 980 kg at the +500 kg rate. The per-kilo figure in the second version looks better and the total is worse.
Adding a little cargo can lower the total. When a consolidation sits close to a band, the useful question is not "what is the rate?" but "what is the total at my weight, and what is the total at the next band?" Ask for both, in total, and compare those. Per-kilo rates on different bands are not comparable numbers.
What else is on an air freight invoice
- Minimum charge per shipment. Every scale has a floor, so small consignments pay as though they were larger. Below roughly 45 kg, a courier contract is usually the cheaper route — and its divisor is harsher, which is why the comparison should be run on totals.
- The origin leg in China. Trucking to the airport, export declaration and local terminal handling are not in an airport-to-airport rate. On a door-to-door quote they appear as a separate fixed figure per shipment rather than as a cost per kilo — and they do not fall when the air rate falls.
- Carrier surcharges. Fuel and security surcharges move with the market and are billed as their own lines, not folded into the kilo rate. A quote that shows one all-in figure per kilo has still priced them in somewhere; ask where.
- Special handling. Dangerous goods, temperature-controlled shipments, oversize pieces, live animals and perishables each carry their own handling, documentation and sometimes approval charges.
- The destination side. Airport terminal handling, customs clearance and inland delivery to the consignee's city are billed in India, normally to the consignee, unless the quote was written as DDP.
Where chargeable weight can actually be moved
- Shrink the carton, not the cargo. For light goods the billable number is the box, so void space is money. Trimming the 60 cm side of the carton above to 50 cm takes 17% off its volumetric weight and changes nothing about the contents.
- Consolidate into one shipment. Chargeable weight is assessed per shipment, so several small consignments each attract the minimum charge and the highest bands. One air waybill, priced once, at a lower band, is usually cheaper than three.
- Confirm the divisor before comparing quotes. A quote built on ÷5,000 prices the same carton 20% heavier than one built on ÷6,000. Two figures that look like the same service can be 20% apart before the rate is even discussed.
- Decide air against sea on cargo value, not on weight. Air normally earns its cost when the goods are high value per kilo and the transit time is the reason for shipping at all. The useful measure is freight cost as a share of cargo value, not USD per kilo on its own.
What our own air files show
Two entries from our desk, because the arithmetic above behaves differently once real shipments are attached to it.
1. The origin leg is a separate number, and it does not move with the kilo rate. In March 2026 we quoted an air shipment from Liaoning, door to door, at USD 7.15 per kg with the origin leg broken out separately at USD 1,250 for trucking, local charges and export declaration. The following day we re-quoted the same shipment at USD 6.35 per kg — an 11% fall on the air rate in 24 hours. The USD 1,250 did not move at all. On a 1,000 kg shipment that fixed leg is worth about USD 1.25 per kilo; on a 100 kg shipment it is USD 12.50 per kilo. This is the arithmetic behind a claim we make often: two door-to-door quotes compared only on the number before "per kg" are not being compared.
2. Real enquiries arrive already sitting on a breakpoint. In September 2026 an Indian forwarder asked us for 1,000 kg of fresh fruit, Guangzhou to Delhi by air, on a regular monthly basis. One tonne is the top of the standard scale, so the rate question and the band question were the same question. What actually decided whether the shipment was workable had nothing to do with chargeable weight: the import permit and the phytosanitary side sits with the importer in India, and the China-side export declaration needs a named exporter entity. Both are commercial arrangements rather than freight calculations — and both had to be settled before a rate was worth quoting at all.
Both entries point the same way. Chargeable weight is arithmetic, and arithmetic is the easy part. The quote around it is a set of separate decisions, and the fixed items are where the surprises live.
How we quote air freight
Send us the carton dimensions, the gross weight, the number of pieces, the airport pair and whether you want airport-to-airport or door-to-door. We will calculate the chargeable weight, quote the total at your actual weight and at the next breakpoint, and show the origin leg as its own line, so you can see which part is measured per kilo and which part is fixed. For the lanes, transit times and equipment on this trade, see China to India air freight; for what gets billed after the aircraft lands, see destination charges at an Indian port.