“My cargo weighed in at 120 kilograms — why does the invoice say 480?” We take this call monthly. The answer is not a padded bill; it is air freight’s first rule: aircraft sell space as much as payload, and light, bulky cargo pays for the space it occupies, converted into weight.
Chargeable weight: actual vs volumetric, whichever is greater
Air freight prices on chargeable weight: the greater of actual and volumetric weight. The IATA convention:
- Volumetric weight (kg) = L × W × H (cm) ÷ 6000
A 100 × 80 × 60 cm box of cushions weighs 20 kg actual, but 480,000 ÷ 6000 = 80 kg volumetric — the invoice reads 80. Multi-piece shipments compute per piece, sum, then compare with total actual weight. Dense hardware ships on actual; textiles, foam and flat-pack furniture are all but guaranteed volumetric.
One aside: couriers (FedEx/DHL) commonly divide by 5000, making the same box heavier in courier terms — a trap when comparing courier against air freight for bulky goods; details in our FedEx dimensional-weight article.
And a legitimate quirk: air tariffs step down by weight break — higher brackets, lower per-kg rates — so cargo sitting just under a break can cost less by declaring into the higher bracket (“as agreed” in trade slang). Ask for it when requesting quotes.
Surcharges: the second bill behind the base rate
The per-kg rate is the skeleton; the invoice adds a surcharge layer, four common types:
- Fuel surcharge (FSC): floats with fuel prices, billed on chargeable weight — in volatile periods it approaches the freight itself
- War-risk / security surcharges: levied on risky airspace or elevated screening costs
- Peak season surcharge (PSS): applied when capacity tightens, starting and stopping at short notice
- Remote, handling and miscellaneous: ground handling, dangerous goods, oversized pieces, remote delivery — per shipment or per piece
The trouble is that every line moves and every forwarder lists differently — some bury surcharges in the rate, some itemize. So the only correct comparison is the all-in total: same cargo, same door-to-door scope, one number with every surcharge included. Compare per-kg rates alone and the surcharge layer flips the ranking.
Three practical moves that shrink chargeable weight
- Reduce the cube: smaller cartons, vacuum compression, knock-down parts packed flat — volumetric weight is computed, and one packaging revision can cut a tier
- Measure before tender: supply your own accurate dimensions and weight; airport re-weighs mean corrected invoices and missed flights
- Consolidate shipments: merge a week’s small orders into one tender — chargeable weight crossing into a higher break can lower the total
Where SKYCARGO fits
SKYCARGO INC quotes air freight all-in — base, FSC, security, seasonal and destination charges in one number — and flags when your cargo profile actually belongs on ocean or courier instead. Get a quote. (Personal parcels: Shiptw.)
Rates and surcharges vary continuously by lane and season; formulas here are industry conventions. Reference only.
