You get a quote for $3 per kg, ship a 50 kg box, and expect to pay $150 — only to receive an invoice for $400. The reason is chargeable weight, and understanding how it works is essential for anyone who ships by air regularly.
What Is Chargeable Weight?
Air freight is priced on chargeable weight, which is the greater of two values: the actual (gross) weight of the shipment, or the volumetric (dimensional) weight. Airlines charge whichever is higher because they are constrained by both the weight capacity and the volume capacity of their aircraft.
How Volumetric Weight Is Calculated
The standard IATA formula: Volumetric Weight (kg) = Length (cm) x Width (cm) x Height (cm) / 6,000
Example: A package measuring 60cm x 50cm x 40cm has a volume of 120,000 cm3. Divided by 6,000 = 20 kg volumetric weight. If the actual weight is 8 kg, the chargeable weight is 20 kg — and you pay for 20 kg.
Why This Matters for Your Shipping Budget
Many light but bulky products (inflatable goods, polystyrene foam, clothing) have volumetric weights that are 3-5x higher than their actual weight. If your forwarder quotes a rate per kg without clarifying the chargeable weight basis, you can easily end up paying far more than expected.
Air Freight Rate Structure
- Base rate per kg — Varies by origin and destination airport pair, commodity, and market conditions. Rates are highly dynamic, sometimes changing daily on key lanes.
- Fuel surcharge (FSC) — A per-kg surcharge that fluctuates with jet fuel prices. Can represent 20-40% of the total freight cost.
- Security surcharge (SSC) — A per-kg charge covering enhanced security screening requirements.
- Airport handling fee — Charged at origin and/or destination airport.
Minimum Charges
Most airlines and freight forwarders apply a minimum charge per shipment — typically the equivalent of 45 kg or 100 kg, regardless of actual or chargeable weight. For very small shipments, this can make air freight disproportionately expensive.
How to Optimise Your Air Freight Costs
- Optimise packaging — reduce external dimensions to lower volumetric weight
- Consolidate shipments to achieve better rate brackets
- Use a neutral air consolidator for LCL air freight
- Book in advance to avoid last-minute premium rates
- Always request all-in quotes including fuel and security surcharges