A calculation in litres misleads, because containers are not fluid; floor area, height and weight each set their own limit. ONE publishes these figures for a standard 20 ft dry box: inside 5,898 × 2,350 × 2,390 mm, door opening 2,340 × 2,280 mm, payload 28,330 kg.
- Width: how many containers fit side by side across the internal width in the chosen orientation.
- Length: how many rows fit along the internal length.
- Height: how many tiers go on; the stack must stay under the door opening.
Multiplying the three gives the count, and no step is rounded up.
Example: a hypothetical container measuring 800 × 600 × 700 mm outside gives 3 × 7 × 3 = 63 with its 600 mm side across the width, and 2 × 9 × 3 = 54 with its 800 mm side across. The choice of orientation is worth nine containers; 290 mm is left in the height.
The weight limit is worked out separately: at 63 containers, up to 449 kg per container stays within 28,330 kg. The CTU Code asks for cargo to be stowed with empty space minimised and for the permitted payload not to be exceeded.
Nesting empties change the calculation: GEBHARDT Rocotec nests up to four high and saves up to 75% of space on the empty return.
