How this calculator works
A shipping container is a fixed box, and cartons inside it fit in whole numbers along each axis. Dividing each internal dimension by the matching carton dimension and multiplying the three quotients gives the count for one orientation. A carton that is 60 by 40 by 30 centimetres can be laid down in six different ways, so the page checks all six and keeps the best. The volume used figure compares the carton volume with the container volume. Real loading is lower because cartons are not perfectly rigid, the door pillasters cut into the opening and workers need gaps to load and unload.
Formula
cartons = floor(container length / carton length) x floor(container width / carton width) x floor(container height / carton height), tried for all six ways of matching the three carton dimensions to the three container axes, keeping the largest. utilisation = cartons x carton volume / container volume.
Worked example
A 20 ft standard container has internal dimensions of 5.898 by 2.352 by 2.393 metres. For 60 by 40 by 30 cm cartons, placing 60 cm along the length gives floor(589.8 / 60) = 9, floor(235.2 / 40) = 5 and floor(239.3 / 30) = 7, which is 315 cartons. The best of the six orientations is 315 cartons, using 68.3 percent of the container volume.
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Frequently asked questions
Why is the container not 100 percent full?
Whole cartons leave leftover space at the edges. Mixed carton sizes, pallets and dunnage can do better or worse. The volume figure is an upper bound on packing efficiency for identical boxes, and real loads usually reach 70 to 90 percent of it.
Can I mix carton sizes?
Not with this page, which assumes every carton is identical. For mixed loads, group similar sizes and load the largest first, or use loading software that searches many arrangements at once.
What about the weight limit?
Containers have a maximum payload, typically around 28 tonnes for a 20 ft and 26 tonnes for a 40 ft box. Dense cargo hits that limit long before the box is full, so check the payload as well as the volume.
Should I leave space near the doors?
Yes. Cargo shifts during transport if it is loose, and a gap at the door makes unloading easier. Many shippers plan for a small air gap and brace the load, which is why the practical count is below the pure volume result.