Anyone renting or buying a container quickly runs into labels such as “20 ft”, “40 ft HC” or “5-metre module”. But what do these terms actually mean in centimetres and kilograms? This guide brings together the standardised dimensions of the most common shipping and site containers – with external sizes, usable internal sizes, door openings, weights and volumes.
Shipping containers to ISO standard
Shipping containers are standardised internationally. The ISO standard fixes external dimensions and corner castings precisely, so that containers can be stacked, lashed and handled worldwide with the same cranes and vehicles. Length is traditionally given in feet: a 20 ft container is 6.058 m long on the outside, a 40 ft container exactly twice that plus a small gap.
The table below summarises the main standard types. The internal dimensions, door openings and weights are approximate values, as they vary slightly depending on manufacturer, build year and condition.
| Type | External L × W × H | Internal (approx.) L × W × H | Door opening (approx.) W × H | Tare weight (approx.) | Payload (approx.) | Volume (approx.) |
|---|---|---|---|---|---|---|
| 10 ft | 2.991 × 2.438 × 2.591 m | 2.83 × 2.35 × 2.39 m | 2.34 × 2.28 m | 1,300 kg | 8,000 kg | 16 m³ |
| 20 ft standard | 6.058 × 2.438 × 2.591 m | 5.90 × 2.35 × 2.39 m | 2.34 × 2.28 m | 2,200–2,300 kg | 28,000 kg | 33 m³ |
| 40 ft standard | 12.192 × 2.438 × 2.591 m | 12.03 × 2.35 × 2.39 m | 2.34 × 2.28 m | 3,700–3,800 kg | 26,500 kg | 67 m³ |
| 40 ft high cube | 12.192 × 2.438 × 2.896 m | 12.03 × 2.35 × 2.70 m | 2.34 × 2.58 m | 3,900–4,000 kg | 26,500 kg | 76 m³ |
All height figures refer to the standard or high cube variants. Beyond these basic types there are numerous special designs such as open-top, flat rack, refrigerated or tank containers, which deviate from the internal dimensions listed here.
High cube vs. standard
The most obvious difference between a standard container and a high cube is the height. A high cube is 2.896 m tall on the outside instead of 2.591 m – that is roughly 30 cm more. Internally this leaves a usable height of about 2.70 m instead of 2.39 m.
These extra 30 centimetres make a clear difference in several use cases:
- Bulky or tall goods fit in more easily, such as machinery or palletised goods stacked in several layers.
- Conversions into living or office space benefit, because after fitting floor and ceiling insulation there is still a comfortable ceiling height left.
- More volume on the same footprint: a 40 ft high cube holds around 76 m³ instead of 67 m³ – on an identical footprint.
Rule of thumb: where ceiling height or maximum volume matters, the high cube is the better choice. Where only footprint and weight matter, the standard container is enough.
Why internal size ≠ external size
The internal dimensions are noticeably smaller than the external ones – and for good reason. This is due to the wall construction from profiled steel sheet (Corten steel), which gives the container its strength.
Specifically, space is lost through:
- Wall thickness and profiling of the side walls (several centimetres per side).
- Floor and roof structure, including the wooden floor panels.
- Corner posts and frame, which form the load-bearing structure.
On the 20 ft container, the 6.058 m external length shrinks to about 5.90 m usable internal length, and the width from 2.438 m to around 2.35 m. The door opening matters too: at approx. 2.34 m wide and 2.28 m high it is slightly smaller than the interior itself. Anyone storing wide or tall items should therefore always plan around the door opening – not just the internal size – as the bottleneck.
Weight & payload
For transport, three weight figures are decisive:
- Tare weight: the empty weight of the container itself.
- Payload: the maximum permissible weight of the cargo.
- Max. gross weight: tare plus payload, i.e. the highest permitted total weight.
| Type | Tare weight (approx.) | Max. payload (approx.) | Max. gross weight (approx.) |
|---|---|---|---|
| 10 ft | 1,300 kg | 8,000 kg | 9,300 kg |
| 20 ft standard | 2,200–2,300 kg | 28,000 kg | 30,480 kg |
| 40 ft standard | 3,700–3,800 kg | 26,500 kg | 30,480 kg |
| 40 ft high cube | 3,900–4,000 kg | 26,500 kg | 32,500 kg |
Notably, despite its double length a 40 ft container can carry hardly more weight than a 20 ft container. The reason is the standardised maximum gross weight of around 30,480 kg. The 40 ft format therefore pays off mainly for voluminous but light goods, while the 20 ft format suits heavy, compact loads.
Note as well that the permitted total weights of the transport vehicle on public roads often further limit the theoretical payload in practice.
Site and modular containers & module dimensions
Alongside the standardised shipping containers, there are site and modular containers built in module form. They serve as offices, break rooms, sanitary units or storage and do not follow such a strict ISO standard. Their dimensions are instead guided by practical room sizes and transportability.
Typical benchmark figures:
- Width: usually approx. 2.44 m, with special sizes up to 3.00 m.
- Height: approx. 2.60–2.80 m externally, giving a room-suitable height inside.
- Length: in fixed module steps that can be coupled together.
| Module length (approx.) | Width (approx.) | Height (approx.) | Typical use |
|---|---|---|---|
| 3 m | 2.44 m | 2.60–2.80 m | Small office, storage, WC unit |
| 4 m | 2.44 m | 2.60–2.80 m | Single office, guard container |
| 5 m | 2.44 m | 2.60–2.80 m | Office, break room |
| 6 m | 2.44 m | 2.60–2.80 m | Larger office, crew room |
| 7 m | 2.44 m | 2.60–2.80 m | Open-plan room, classroom |
The big advantage of modular construction is coupling: several containers can be joined side by side and on top of one another into larger, connected units – from a two-storey office landscape to a temporary school. Partition walls are removed so that a continuous room is created.
Which size for what?
- 10 ft: Ideal where little standing space is available – as a tool, garden or building-site store.
- 20 ft: The all-rounder for moves, heavy goods and medium-sized storage tasks; easy to transport and position.
- 40 ft: For large, voluminous quantities and long goods; the maximum volume per container.
- 40 ft high cube: When extra height is also needed – for example when converting to living or office space.
- Site container modules: For anything where people spend time: office, break room, sanitary facilities, teaching.
You can read how the different sizes differ in price in the article What does a container cost?.
Conclusion
Choosing the right container size depends less on the label than on the actual dimensions. What counts is the usable internal size, the often overlooked door opening and – for transport – the permitted payload. Shipping containers are strictly standardised and therefore easy to plan with, while site container modules can be coupled flexibly. Anyone who consults the tables compiled here before renting or buying avoids nasty surprises and reliably finds the right size for their project.