Every new hire memorises the nominal figures and then loses money on the difference between nominal and usable.
01The standard boxes
| Type | Internal (L×W×H, m) | Nominal CBM | Usable CBM | Max payload |
|---|---|---|---|---|
| 20' GP | 5.90 × 2.35 × 2.39 | 33 | 26–28 | ~28,000 kg |
| 40' GP | 12.03 × 2.35 × 2.39 | 67 | 55–58 | ~26,500 kg |
| 40' HC | 12.03 × 2.35 × 2.69 | 76 | 64–68 | ~26,500 kg |
| 45' HC | 13.56 × 2.35 × 2.69 | 86 | 72–76 | ~26,000 kg |
Usable is 10–15% below nominal because pallets do not tessellate, cartons need clearance, and you cannot load into the last few centimetres under the roof.
02Specialised equipment
- Reefer (RF) — temperature controlled, typically −25°C to +25°C. Internal volume is smaller because of insulation. Needs power at the terminal and on board; plug-in charges apply.
- Open Top (OT) — tarpaulin roof for over-height cargo loaded by crane.
- Flat Rack (FR) — no sides, for over-width or heavy machinery. Out-of-gauge surcharges apply.
- Tank — bulk liquids, with its own regulatory regime.
- Ventilated — for cargo like coffee or cocoa that must breathe.
03The weight limits that catch people
There are three different limits and the lowest one binds:
- Container max payload — stencilled on the door. Roughly 28 t for a 20', 26.5 t for a 40'.
- Road legal limit — in Thailand, the combined vehicle weight limits mean a 20' is often capped nearer 22–24 t for inland haulage, depending on the chassis and axle configuration.
- Terminal or line restriction — some terminals and some lanes impose their own caps.
A 20' loaded to 28 t at the factory that cannot legally travel on the road is a very expensive mistake to unwind.
04Choosing between 40' GP and 40' HC
The HC is 30 cm taller — about 9 extra CBM — for a small rate premium. Take the HC unless the destination has a height restriction (some inland routes, some warehouse docks) or the cargo is weight-limited anyway. On volumetric cargo the HC is almost always the better cost per CBM.
05Loading discipline
- Distribute weight evenly; an unbalanced box is a road safety issue and a terminal rejection risk.
- Brace and dunnage against movement — most claims we see are shifted-cargo damage, not water ingress.
- Photograph the load at three stages: empty container with door number visible, half loaded, fully loaded before sealing. Those photos settle claims.
- Record the seal number on the packing list and the B/L. A broken or mismatched seal at destination is an immediate customs hold.