Express couriers divide by 5000; air freight divides by 6000. A 60 × 50 × 40 cm carton is 24 kg by courier math and 20 kg by air math. The divisor is the whole argument — everything else is arithmetic.
The formula
Volumetric weight (kg) = length × width × height in cm ÷ divisor. Use 5000 for express couriers and 6000 for air freight. Then compare with the actual weight: the chargeable weight is whichever is higher.
Worked example 1: a light carton
One carton, 60 × 50 × 40 cm, actual weight 12 kg.
- Volume: 60 × 50 × 40 = 120,000 cm³.
- Courier math: 120,000 ÷ 5,000 = 24 kg.
- Air freight math: 120,000 ÷ 6,000 = 20 kg.
- Chargeable weight: 24 kg by courier, 20 kg by air — both are double the actual 12 kg.
Light, bulky cargo pays for air, not weight. This carton costs twice as much to fly as its scale weight suggests.
Worked example 2: a heavy carton
One carton, 100 × 80 × 60 cm, actual weight 45 kg.
- Volume: 100 × 80 × 60 = 480,000 cm³.
- Courier math: 480,000 ÷ 5,000 = 96 kg.
- Air freight math: 480,000 ÷ 6,000 = 80 kg.
- Chargeable weight: 96 kg by courier, 80 kg by air — against 45 kg actual.
Even a heavy carton can be charged on volume. At 45 kg actual, this box is dense — and it still bills at 80–96 kg, because it takes up the space of two such weights.
Who uses which divisor
- ÷ 5000: DHL Express, FedEx, and UPS for international express. This is the number to use for courier quotes.
- ÷ 6000: air freight under the IATA standard. This is the number to use for airport-to-airport air cargo.
- Other divisors exist. Some regional and domestic couriers use ÷ 4000 or ÷ 6000. The divisor is a commercial choice, not a law of physics — always check the carrier’s own rule before quoting a customer.
The divisor is why the same box costs different amounts on different services. The box does not change; the carrier’s math does.
How to lower the chargeable weight
- Shrink the carton. A carton 5 cm smaller on each side can cut volumetric weight by 20–30%. Right-size packaging before you blame the freight rate.
- Split the shipment. Two small cartons sometimes bill lower than one big one, because the rounding works in your favor — check both ways.
- Compress soft goods. Vacuum-packing textiles or pillows cuts volume directly, and volume is what you pay for.
- Compare courier and air. For the same box, air freight math (÷ 6000) is 17% cheaper than courier math (÷ 5000) on volume alone — before the rate per kg is even considered.