Costs
Chargeable Weight in Air Freight: Volumetric Weight Explained
Airlines sell space in an aircraft hold, and that space runs out in two ways: the aircraft can reach its weight limit, or it can simply fill up. Chargeable weight is how the industry prices both risks with one number. If you understand how it is calculated, you can predict your freight bill before you book and often reduce it with nothing more than a better box.
Key takeaways
- Chargeable weight is the greater of the actual (gross) weight and the volumetric weight of the shipment.
- Under the IATA standard, volumetric weight is the volume in cubic centimetres divided by 6,000, which equals 166.67 kg per cubic metre.
- Express integrators commonly use a divisor of 5,000 for international services, which makes the same box "heavier". Check the divisor in your own contract.
- Rates fall as you move into higher weight breaks, so paying for a slightly higher weight can cost less than the actual weight at the lower break.
- Reducing empty space in your packaging is the most reliable way to cut the bill on light, bulky goods.
Gross weight and volumetric weight
Gross weight is what the shipment weighs on a calibrated scale: goods, inner packing, cartons, strapping and the pallet itself. It is the figure in the weight box of the air waybill, and the handling agent will check it at acceptance. If your declared weight and the scale disagree, the scale wins.
Volumetric weight (also called dimensional weight) is a notional weight derived from the space the shipment occupies. It answers the question: "If this cargo had a typical density, how much would it weigh?" A carton of polystyrene cups weighs almost nothing, yet it takes the same space as a carton of bolts. Volumetric weight makes sure the airline is paid for that space.
The IATA divisor: 6,000 cm³ per kg
The standard formula for general air cargo is:
Volumetric weight (kg) = Length (cm) × Width (cm) × Height (cm) ÷ 6,000
Turn it around and you get the same rule in cubic metres: one cubic metre is 1,000,000 cm³, and 1,000,000 ÷ 6,000 = 166.67 kg. Forwarders often call this the "1:6" ratio, meaning one cubic metre is treated as roughly one-sixth of a tonne. If your cargo is denser than about 167 kg per cubic metre, you pay on actual weight. If it is lighter, you pay on volume.
Express and courier divisors
Express integrators commonly use 5,000 cm³ per kg for international shipments, which works out to 200 kg per cubic metre. The smaller divisor produces a higher volumetric weight for the same box. Some carriers use other divisors for particular products or domestic services, and negotiated contracts can differ from published terms, so always check the figure that applies to your account. Our guide to air freight versus express courier covers the wider differences between the two models.
The chargeable weight rule
Chargeable weight is simply the higher of the two figures. For general air cargo it is then usually rounded up to the next half kilogram, so 84.1 kg becomes 84.5 kg and 84.6 kg becomes 85 kg. Express carriers often apply their own rounding steps, which may be coarser.
How to measure correctly
Measure the outermost dimensions of each piece as it will be handed over: the longest length, the widest width and the tallest height, including any pallet, overhanging cartons, handles or bulging sides. A pallet is measured from the floor to the highest point of the load, so the 14 to 15 cm of a standard wooden pallet base counts.
Carriers state how dimensions are rounded. A common rule for air cargo is to round each measurement to the nearest whole centimetre, but some carriers round every fraction up. The difference looks trivial, yet on a large consignment a single centimetre on each side of each pallet adds up.
Three worked examples
Example A: a dense carton of machine parts
One carton, 60 × 40 × 40 cm, gross weight 84.3 kg.
- Volume: 60 × 40 × 40 = 96,000 cm³
- Volumetric weight: 96,000 ÷ 6,000 = 16 kg
- Gross weight (84.3 kg) is higher, so it applies
- Rounded up to the next 0.5 kg: chargeable weight 84.5 kg
Even with a 5,000 divisor the volumetric weight would only be 19.2 kg. Dense goods like metal parts, tiles or printed paper are almost always charged on actual weight, so better packaging will not change the bill much.
Example B: a light, bulky box of foam and textiles
One box, 100 × 60 × 80 cm, gross weight 14.3 kg.
- Volume: 100 × 60 × 80 = 480,000 cm³
- Volumetric weight: 480,000 ÷ 6,000 = 80 kg
- Volumetric weight (80 kg) is higher than gross (14.3 kg)
- Chargeable weight 80 kg
The shipper pays for more than five times the actual weight. With an express divisor of 5,000, the same box would be 480,000 ÷ 5,000 = 96 kg. Suppose the contents could be compressed into a box of 80 × 60 × 60 cm instead: 288,000 cm³ ÷ 6,000 = 48 kg. Same goods, 32 kg less to pay for.
Example C: a three-pallet consignment
Three pallets moving on one air waybill, for example 235-94456121, measured including the pallet bases:
| Piece | Dimensions (cm) | Volume (cm³) | Volumetric (kg) | Gross (kg) |
|---|---|---|---|---|
| Pallet 1 | 120 × 80 × 150 | 1,440,000 | 240 | 195 |
| Pallet 2 | 120 × 80 × 150 | 1,440,000 | 240 | 195 |
| Pallet 3 | 120 × 100 × 110 | 1,320,000 | 220 | 260 |
| Total | 4,200,000 | 700 | 650 |
Total volume is 4.2 m³, and 4,200,000 ÷ 6,000 = 700 kg (cross-check: 4.2 × 166.67 ≈ 700). Total gross weight is 650 kg. The chargeable weight is 700 kg.
Notice that pallet 3 is dense on its own (260 kg actual against 220 kg volumetric). Airlines normally compare the totals for the whole consignment, not piece by piece, so pallet 3's density offsets some of the volume of the other two. Had pallet 3 been shipped on a separate AWB, it would have been charged at 260 kg, and the other two at 480 kg, for 740 kg in total. Consolidating pieces of different density on one waybill can therefore help.
Weight breaks and rate classes
Air cargo tariffs are not a single price per kilo. They are built around rate classes, and the main ones you will see on a rate sheet or on the AWB are:
- M (minimum charge): the lowest amount the airline will accept for a shipment, however small.
- N (normal rate): the rate per kg for shipments under 45 kg.
- Q (quantity rates): lower rates per kg at weight breaks. Typical breaks are +45, +100, +300, +500 and +1,000 kg, although the exact breaks vary by airline and route.
Specific commodity rates and class rates (surcharges or reductions for categories such as live animals or valuables) also exist but most general cargo is priced on N and Q rates.
When a higher weight break is cheaper
Because rates drop at each break, the charge for a shipment just under a break can exceed the charge at the break itself. Airlines allow the lower rate to be applied to the break weight if that produces a lower total. Using purely illustrative rates:
| Calculation | Weight charged | Illustrative rate | Charge |
|---|---|---|---|
| Actual chargeable weight at +45 rate | 88 kg | 3.20 per kg | 281.60 |
| Next break at +100 rate | 100 kg | 2.70 per kg | 270.00 |
Charging 100 kg at the +100 rate saves 11.60. The break-even point is 270.00 ÷ 3.20 = 84.375 kg. With chargeable weight in 0.5 kg steps, any shipment from 84.5 kg up to 100 kg is cheaper billed at 100 kg: 84.5 × 3.20 = 270.40, which already exceeds 270.00. Good forwarders and rating systems apply this automatically, but it is worth checking on manual quotes.
Packing to reduce volumetric weight
- Right-size the carton. Empty space is paid for at the same rate as goods. Standard box sizes that leave a 10 cm gap on every side are expensive by air.
- Compress soft goods. Textiles, cushions and foam can often be vacuum-packed or compressed without damage.
- Ship flat-packed or nested. Furniture, shelving and buckets that nest take a fraction of their assembled volume.
- Do not overbuild pallets. Keep cartons within the pallet footprint; overhang raises the measured length and width and invites damage.
- Watch the height. A tall, narrow pallet may need to be treated as non-stackable, and some carriers may charge non-stackable freight for the space above it that cannot be used.
- Combine dense and light items on one AWB when they travel to the same consignee, as in Example C.
Before you book, run your dimensions through the chargeable weight calculator with both the 6,000 and 5,000 divisors. If the two results differ widely, the choice between air freight and express is partly a packaging question.
Where chargeable weight appears on the paperwork
On an air waybill, the chargeable weight sits next to the rate class and the rate in the charges section, separate from the gross weight. Volume or dimensions are shown in the nature and quantity of goods box. If the two weights on your invoice do not match what you expected, compare them with the AWB; our guide on how to read an air waybill explains each box.
Tracking the shipment once it is booked
Chargeable weight decides what you pay; the air waybill number decides how you follow the cargo. Once your forwarder gives you the AWB, enter it in the free tracking lookup on AWBTracking.net to see booking, departure and arrival events, and the piece count and weight the airline has recorded against your shipment.