Container loading calculator

How many flat-pack units — or panels, or crates — fit in a 20ft or 40HQ container, and what limits the load: volume or payload. No dependencies, one file.

python3 container_loading.py 40hq 2900 2200 600 900

{
  "container": "40ft high cube",
  "units_per_layer": 4,
  "layers": 4,
  "units_by_volume": 16,
  "units_by_payload": 31,
  "units": 16,
  "limited_by": "volume",
  "volume_utilisation_pct": 80.2,
  "payload_utilisation_pct": 50.3
}

The same unit in a 20ft, with a heavier unit, is weight-limited instead:

python3 container_loading.py 20gp 1000 1000 500 5000
# units_by_volume 40 · units_by_payload 5 · units 5 · limited_by "weight"

Options

flag	what it does
--max-layers N	caps the number of layers when the packing method limits stacking
--rotate	tries rotating each unit 90° and uses whichever fits more per layer

Why it refuses to calculate

If the packed length, width, height or the unit weight is missing, the tool raises an error listing exactly what is missing instead of returning a number. A guessed loading plan is how deposits get lost — the packed height and the unit weight are the two inputs that move the answer most, and both come from the factory packing method.

Container data used

Typical published internal dimensions and payloads. Confirm against the carrier's own data and the actual packing list before booking.

container	internal L × W × H (mm)	payload (kg)
20ft GP	5898 × 2352 × 2393	28,200
40ft HQ	12032 × 2352 × 2698	28,600

Volume utilisation is calculated on the packed envelope (length × width × height of one unit), not on the net product volume.

Web version

Same logic, in the browser, no install: container loading calculator — the tool we use ourselves when quoting flat-pack buildings and aluminium ceiling systems.

Tests

python3 tests/test_loading.py

License

MIT