How to Calculate Volumetric Weight (and Why Carriers Charge It)
You weighed your parcel: 5 kilograms. The airline billed it at 42. You're not being scammed — you're meeting volumetric weight, the single most misunderstood number in freight. Here's the math, so the next invoice holds no surprises.
The formula
- •Air freight: volumetric weight (kg) = CBM × 167
- •Express courier: volumetric weight (kg) = L × W × H (cm) ÷ 5,000
- •CBM = L × W × H (cm) ÷ 1,000,000 per carton, × carton count
- •You are charged on: max(actual weight, volumetric weight)
Worked example — the 42 kg '5 kg' parcel
A 60 × 50 × 50 cm carton weighs 5 kg actual. Its volume is 0.15 CBM. By air: 0.15 × 167 = 25 kg volumetric. By express: 60 × 50 × 50 ÷ 5,000 = 30 kg. The carrier charges the higher of actual versus volumetric — so your 5 kg physical parcel bills at 25–30 kg. The scale was never the point; the space on the aircraft was.
Why the divisor differs by mode
The divisor encodes each mode's economics. Aircraft cargo density runs around 167 kg per cubic meter — hence air's multiplier. Courier networks use 5,000 (equivalent to 200 kg/m³) because van-and-sorted networks are even more space-constrained. Sea containers pack 800–1,000+ kg per CBM, which is why ocean freight barely notices your volumetric weight and charges by volume instead.
- •Air (×167): space-starved but weight-capable
- •Express (÷5,000): most space-sensitive divisor
- •Sea LCL: billed per CBM — volume IS the weight
- •Sea FCL: the whole box is yours; per-unit math stops mattering
How to defend yourself
- •Calculate before quoting: our homepage calculator does both weights instantly
- •Challenge re-weighs: ask for the dimensions used, and re-measure the carton yourself
- •Pack denser: heavier cartons within limits can move you from volumetric to actual billing
- •Mode-shift: if volumetric dominates, sea LCL is usually the cure