Your air freight invoice is almost never built on what the cargo weighs on the scale. It is built on chargeable weight, which is the higher of actual weight and volumetric weight, and that is why an air freight chargeable weight calculator is the first thing to reach for when a quote looks wrong. Sea freight uses a different comparison but the same idea: the carrier charges for whichever the shipment consumes more of, weight or space.
Everything below is arithmetic you can check yourself. The numbers in the examples are ours, constructed to show the method. They are illustrations, not rates, and they are not what any carrier will quote you.
Air: actual weight against volumetric weight
Volumetric weight converts the space a package occupies into a notional weight, so a light bulky carton pays for the hold space it blocks. The formula is:
Volumetric weight (kg) = length × width × height in cm ÷ the divisor
The divisor is the number that turns cubic centimetres into kilograms. General air cargo has conventionally used 6000, which is the same as saying 1 CBM is treated as 166.67 kg. Express and courier traffic commonly uses 5000, which treats 1 CBM as 200 kg and therefore produces a higher chargeable weight for the same box. Some carriers and lanes use their own figure. Confirm the divisor before you accept a quote, because it changes the invoice more than the rate per kilo does.
Worked example, air (illustration only)
Six cartons of packaging components, each 60 × 45 × 50 cm, each weighing 9 kg.
- Actual weight: 6 × 9 = 54 kg
- Volume per carton: 60 × 45 × 50 = 135,000 cm³
- Total volume: 135,000 × 6 = 810,000 cm³, which is 0.81 CBM
- Volumetric weight at divisor 6000: 810,000 ÷ 6000 = 135 kg
- Volumetric weight at divisor 5000: 810,000 ÷ 5000 = 162 kg
Chargeable weight is 135 kg on the 6000 divisor and 162 kg on 5000. The scale still says 54 kg. You are paying for two and a half to three times the actual weight, and the difference between the two divisors alone is 27 kg on one small consignment.
The other direction
Reverse the cargo and the answer flips. Four cartons of pharmaceutical raw material, each 40 × 30 × 30 cm, each 28 kg.
- Actual weight: 4 × 28 = 112 kg
- Total volume: 36,000 × 4 = 144,000 cm³, which is 0.144 CBM
- Volumetric weight at 6000: 144,000 ÷ 6000 = 24 kg
Chargeable weight is 112 kg, the actual weight, because dense cargo consumes weight allowance faster than space. This is why chemicals, dyes and pharma intermediates out of Ahmedabad usually charge on actual weight while textiles, garments and ceramics samples charge on volume.
Rounding and per-piece rules
Three details change the final figure and are easy to miss:
- Rounding. Airlines typically round chargeable weight up to the next 0.5 kg, and many round each dimension to the nearest whole centimetre first. A carton measured at 60.4 cm may be billed at 61 cm.
- Measure the package, not the product. Pallet height includes the pallet. Shrink wrap, corner boards and overhang all count. A 100 × 120 cm pallet that bulges to 105 × 125 cm is measured at the bulge.
- Comparison is usually per consignment, not per carton. Total actual weight against total volumetric weight for the whole shipment as tendered under one air waybill.
Sea: CBM against the weight tonne
LCL sea freight uses W/M, weight or measurement. The carrier compares the shipment’s volume in cubic metres against its weight in tonnes and charges on whichever number is higher, treating 1 CBM and 1,000 kg as equivalent revenue tonnes.
CBM = length × width × height in metres, added across all pieces. Then compare that figure to gross weight divided by 1,000.
Worked example, LCL (illustration only)
Twelve cartons of finished textiles, each 0.8 × 0.6 × 0.5 m, each 22 kg.
- Volume per carton: 0.24 CBM. Total: 12 × 0.24 = 2.88 CBM
- Gross weight: 12 × 22 = 264 kg = 0.264 tonnes
- W/M basis: 2.88 against 0.264, so you are billed on 2.88 revenue tonnes
Now the same twelve cartons filled with ceramic tiles at 95 kg each: volume stays 2.88 CBM, weight becomes 1,140 kg or 1.14 tonnes. Volume still wins. Tile and granite shippers only cross into weight-basis billing at densities above one tonne per cubic metre, which is why heavy stone moves FCL and light finished goods move LCL.
| Mode | What is compared | Equivalence used | Billed on |
|---|---|---|---|
| Air, general cargo | Actual kg vs volume | 1 CBM treated as 166.67 kg (divisor 6000) | Higher of the two, rounded up |
| Air, express | Actual kg vs volume | 1 CBM treated as 200 kg (divisor 5000) | Higher of the two, rounded up |
| LCL sea | CBM vs weight tonne | 1 CBM treated as 1,000 kg | Higher of the two, per revenue tonne |
| FCL sea | Neither | Not applicable | Per container, subject to payload limits |
FCL is the exception that proves the point. You buy the box, so volume and weight stop competing. They reappear as constraints instead: the container’s maximum payload, and any road weight limit on the haul from Ahmedabad or Morbi to Mundra or Pipavav.
Using an air freight chargeable weight calculator properly
An air freight chargeable weight calculator only returns the right answer if you feed it the right inputs. Before you trust the output:
- Measure the packed, palletised pieces as they will be tendered, not the inner cartons.
- Confirm the divisor your carrier is applying on that lane. Ask, do not assume 6000.
- Enter gross weight, including pallet, dunnage and packaging.
- Group by piece type where cartons differ, then total.
- Compare the result against the chargeable weight printed on the air waybill. If they differ, the dispute is about measurement or rounding, and it is winnable with photographs and a measurement sheet.
Our CBM calculator runs both comparisons from the same dimensions, so you can see the air and sea answer side by side before you decide which mode to use.
What this changes about how you pack
- Reduce void space before you negotiate rate. Cutting carton height by 5 cm across a shipment usually saves more than arguing over the per-kilo rate.
- Check whether the pallet earns its place on air. A pallet adds height and weight to every calculation. On short air runs, slip sheets or floor-loading can remove several chargeable kilos.
- Mixed density cargo consolidates well. Pairing dense chemical drums with light textile cartons in one consolidation balances weight against volume so neither is wasted.
- Model both modes before committing. A shipment that is volumetric on air may be weight-neutral on LCL, and the mode decision should be made on chargeable figures, not gross weight.
Once you know the chargeable weight, the rest of the cost stack follows: terminal handling, documentation, clearance and duty. How those arise in sequence is set out in the customs clearance process in India, and how GST attaches to the freight line is covered in GST and HSN on air and ocean freight. Compare the modes themselves under air freight and ocean freight.
Talk to Scapex
Send us your carton dimensions and gross weights and we will return the chargeable weight for both air and LCL, with the divisor and the rounding shown, so you can see exactly what your invoice will be built on. Contact Scapex with your packing list.