Container loading calculator
How many plates fit in a 20′ or 40′ box, and whether volume or payload decides it. Useful before you fix a cut length.
Cargo
Container
Two limits run in parallel: the box volume and the container payload. The answer is whichever runs out first — and which one it is changes how you should plan.
Plate weight (kg) = L × W × t × ρ / 109Plates by weight = payload (kg) / plate weightPlates by space = pieces per layer × stackable layers
| Container | Internal volume | Practical payload |
|---|---|---|
| 20′ GP | ≈ 33 m³ | 21 – 25 t |
| 40′ GP | ≈ 67.7 m³ | 23 – 27 t |
| 40′ HQ | ≈ 76 m³ | 23 – 27 t |
| 20′ flat rack | open top / sides | 27 t + |
| Breakbulk | no limit | best over 12 m |
- Watch the 20′ box: internal length is only 5,898 mm, so 6,000 mm plate does not fit. It is the most common loading mistake we see.
- Thick plate almost always hits the payload limit first; thin sheet hits the volume limit.
- Ask for a loading plan with the quote. A poor plan costs 10–15% of the fill.
People also ask
Which usually limits a plate shipment — volume or weight?
Weight for anything over about 8 mm, volume for thin sheet. Aluminium is light for its bulk, so a container fills up with tonnage before it fills up with volume on thick plate.
What is the real payload of a 20′ container?
Rated around 28 t, but road transport limits usually cap it at 21–25 t. Always quote the payload you can actually move, not the container rating.
Can a 6,000 mm plate go in a 20′ container?
No — and this catches people out constantly. A 20′ container is only about 5,898 mm long internally, so a 6 m plate simply does not fit. Order in 40′ containers, or cut to under 5,800 mm.
Can I ship 12 m plate in a container?
Only in a 40′ container, and only just: internal length is 12,032 mm, so 12 m plate leaves 32 mm for packing and dunnage. Over 11.5 m, plan on a flat rack or breakbulk.
How much does dunnage and lashing reduce the load?
Plan on 5–10%. Wooden dunnage between layers, steel strapping and corner protection all take space that a pure volume calculation ignores.
Do you supply a loading plan?
Yes — we provide a loading plan and photographs of the loaded container for every shipment.
What about moisture damage in transit?
Aluminium does not rust, but white oxide staining on mill finish is a common claim. Desiccant bags and VCI wrap on the top layer are standard for long sea legs.
Need plate to match these numbers?
Reply in one working day with stock availability and a firm price.
