Chargeable weight: the number that decides your air freight bill
Airlines do not charge by weight. They charge by chargeable weight, which is whichever is greater: your actual weight, or your volumetric weight. Volumetric weight is your volume in cubic centimetres divided by 6,000 — which works out to roughly 167 kg per cubic metre.
The practical consequence: if a cubic metre of your cargo weighs less than 167 kg, you are paying for space you are not using. Coir, garments, packaging and empty containers of anything are punished badly. Cashew kernels, spices, machinery parts and seafood are dense enough that actual weight usually governs, which makes air far more competitive than exporters expect.
Sea freight works the opposite way for LCL, charging on whichever is greater of one cubic metre or one tonne — the "W/M" basis. Dense cargo pays by weight, light cargo pays by volume.
The cost everyone forgets
A shipment worth ₹50 lakh sitting on the water for an extra 25 days is ₹50 lakh you cannot spend, at whatever your working capital costs you. At 12% a year that is around ₹41,000 of real money — before you count the risk of a missed season, a cancelled order, or a buyer who pays 30 days after arrival rather than 30 days after departure.
This tool adds that carrying cost to the sea option, which is why its answer sometimes differs from what a freight forwarder will tell you. Forwarders quote freight. They do not quote your balance sheet.
The number worth remembering from your result is the break-even cargo value — the invoice value above which flying it is genuinely the cheaper decision once capital is counted.
When air wins regardless of the maths
- Perishables. Fresh seafood, flowers, fruit and vegetables do not survive a sea transit. The calculation is not a calculation.
- Samples and first orders. The cost of losing a new buyer to a slow first shipment dwarfs the freight difference.
- A deadline that is real. If the sea option physically cannot arrive in time, its price is irrelevant.
- High value, low weight. Ayurvedic extracts, spice oleoresins, electronics, jewellery — where freight is a rounding error against cargo value.
- Peak-season stockouts. Missing a selling window costs more than the premium.
When sea wins and it is not close
- Anything bulky and cheap per kilo — coir, timber, tiles, raw rubber, packaging.
- Full container loads. Once you fill a 40ft, the per-kilo economics are unbeatable.
- Regular replenishment where you can plan around the transit.
Kerala's four airports
Cochin (COK) handles the most cargo and has the widest network, including dedicated perishable handling. Trivandrum (TRV) serves the south and is the natural choice for Kollam, Trivandrum and the Tamil Nadu border districts. Calicut (CCJ) covers Malabar, and Kannur (CNN) the far north. This tool routes you through whichever is nearest and prices the road leg accordingly — the same way it picks between Vizhinjam and Cochin for sea.