The question is never simply "which is cheaper". Air and sea freight are priced on different units, and they consume different amounts of your money in places that do not appear on the freight invoice.
How each mode is priced
Sea freight is priced by volume for LCL (per revenue ton, meaning the higher of cubic metres or tonnes) and by container for FCL. A 20-foot box holds roughly 28 CBM of usable space; a 40-foot high cube around 65 CBM. Once you fill a container, the marginal cost of the next cubic metre is close to zero, which is why sea freight rewards volume.
Air freight is priced on chargeable weight - the greater of the actual weight and the volumetric weight. Most carriers use a divisor of 6,000 for dimensions in centimetres, so one cubic metre equals roughly 167 kilograms. A light, bulky carton therefore pays for airspace it does not weigh, while a dense item such as machine parts pays for its real kilos.
The real comparison is total cost
A useful comparison adds three things to the freight rate:
- Speed of cash conversion. Sea freight adds weeks between paying your supplier and receiving your goods. That is capital sitting still, plus warehousing at destination.
- Stock-out risk. If a production line stops or a promotion misses its window, the cost of waiting is far larger than the air premium.
- Handling and damage. Air cargo is handled more times but in smaller units and under cover. Sea containers travel for weeks through humidity swings.
As a rough rule: the higher the value density - rupiah per kilogram - the more air freight pays for itself. Electronics, pharmaceuticals, cosmetics, spare parts and fashion move by air for that reason. Furniture, building materials, machinery and bulk commodities almost never do.
Where the decision usually lands
For shipments above roughly two to three tonnes, sea freight is almost always cheaper in absolute terms. Below a few hundred kilograms, air is often competitive once you include the handling minimums and documentation on the sea side. In between, it depends on how urgently the buyer needs the goods.
A practical compromise is to split the shipment: send a small air consignment to start production or fill the shelves, and the bulk by sea. This is common for seasonal goods and new product launches from Batam.
Constraints people forget
Air has hard limits that no amount of money removes: aircraft dimension restrictions, dangerous goods rules for lithium batteries and aerosols, and security screening cut-offs that are earlier than the flight. Sea has its own: port congestion, blank sailings and container availability during peak season.
How ISL Group helps
We quote air and sea side by side, including chargeable weight, so you can see the real difference rather than two numbers in different units. Send us the dimensions, actual weight and deadline, and we will tell you where the break-even sits for your cargo.
