CBM and chargeable weight
Home — CBM and chargeable weight
Why the weight on the invoice is often not the weight on the scale.
Two numbers describe every consignment
One is what the cargo weighs. The other is how much room it takes up. A carrier sells space and it sells payload, and it will charge you on whichever of the two runs out first.
That is the whole idea behind chargeable weight, and it is the single most common surprise on a first invoice. A pallet of insulation panels weighs almost nothing and fills half a container; a pallet of tiles does the opposite. Priced on weight alone, one of those two is being carried for free.
CBM — the space
Sea freight is quoted against cubic metres, and it is the figure a consolidator prices a part-load on.
Cubic metres
L × W × H (cm)
1,000,000
Measure the outside of the packed carton, not the goods inside it. Pallet feet and shrink wrap are chargeable space.
Worked example
Length 120 cm
Width 80 cm
Height 100 cm
(120 × 80 × 100) ÷ 1,000,000
Volumetric weight —
Air freight is sold by weight, so volume has to be turned into a weight before it can be priced.
Volumetric weight (air)
L × W × H (cm)
6,000
6,000 is the common air freight divisor. It varies by carrier and by contract — read the one on your rate sheet before you budget.
The same box, by air
Length 120 cm
Width 80 cm
Height 100 cm
(120 × 80 × 100) ÷ 6,000
Chargeable weight —
The carrier takes the higher of the two figures. Nothing else about the shipment changes it.
The rule
Chargeable weight = the higher of actual weight and volumetric weight
For our box: the scale says 120 kg, the volume says 160 kg, so the invoice is raised on 160 kg — a third more than the scale suggested.
Which figure wins
Actual weight 120 kg
Volumetric 160 kg
The higher of the two is charged.
The rest of the arithmetic
The figures a forwarding desk works out a dozen times a day, in the form they are actually used.
Total CBM for a consignment
CBM per carton × number of cartons
Container utilisation
Total CBM
Container CBM
Multiply by 100 for a percentage. Under about 70% and a smaller box, or a part-load, is usually cheaper.
Freight cost per CBM
Total freight
Total CBM
Freight cost per kg
Total freight
Total gross weight
Pallet count
Total CBM
CBM per pallet
Gross weight
Net weight + tare weight
Net is the goods, tare is the packing, pallet and container. Added, not divided — a widely-shared chart gets this one wrong.
TEU
A 20′ box is 1 TEU · a 40′ box is 2 TEU
Sea transit time
Distance (nautical miles)
Average speed (knots)
A knot is one nautical mile per hour, so this gives HOURS. Divide by 24 for days, then add port time at both ends.
CBM and chargeable weight — the one-page version
The whole guide on a single sheet, sized for WhatsApp and for A4. Ours to give away.