"Should we fly it or ship it?" is one of the most common questions in logistics. The honest answer is: it depends on weight, value, urgency and total cost — not just the freight rate.
The Core Trade-off
Air freight moves in days and is gentle on cash-flow-sensitive or perishable goods, but the rate per kilo is high. Ocean freight moves in weeks and is dramatically cheaper per kilo, but ties up inventory in transit and adds port/CFS time at both ends.
Chargeable Weight: the Maths That Surprises People
Carriers charge on the greater of actual weight or volumetric (dimensional) weight. For air freight the common formula is length × width × height (cm) ÷ 6000 = volumetric kg. So a light but bulky box is billed as if it were heavier. Ocean freight uses the "W/M" rule — the greater of weight in tonnes or volume in CBM. Knowing which applies tells you instantly whether your cargo is "light and bulky" (bad for air) or "small and dense" (air-friendly).
Think Total Landed Cost, Not Freight Rate
- Inventory carrying cost. Six weeks on the water is six weeks of capital tied up.
- Insurance & risk. Longer transit = more exposure.
- Packaging. Ocean often needs sturdier, heavier packing.
- Speed-to-market. For fashion, electronics or launches, being late can cost more than the freight saved.
A Simple Decision Framework
Lean air when: the cargo is high-value-to-weight, urgent, perishable, or small enough that the rate difference is modest. Lean ocean when: the cargo is heavy or bulky, cost-sensitive, and you can plan ahead. Many supply chains blend both — ocean for the baseline, air for top-ups and emergencies.
Sources & Further Reading
- IATA — air cargo volumetric weight standard (÷6000 rule).
- Industry "W/M" (weight or measurement) convention for ocean freight.
- ICC Incoterms® 2020 — for who bears freight and risk in each mode.
