Container Dimensions Explained: 20ft, 40ft, High Cube, Reefer

Container dimensions come in three kinds, and only one of them tells you how much cargo fits. The nominal size (the 20’ or 40’ in the name) is a label. The external dimensions are the outside measurements, fixed by standard so every box fits the same ships, trucks and cranes. The internal dimensions, together with the door opening, are the space you can actually load, and that is what a load plan should start from.

The figures below are typical values. Individual containers differ by a few centimeters depending on the manufacturer and when they were built, and even shipping lines publish their specs as examples rather than guarantees. For a sortable version of the full spec table, see our container specifications page.

Container dimensions by type#

Capacity is the nominal figure quoted for each type. The 20’ and 40’ standard rows are dry containers.

The differences between shipping lines are small. One line’s 20’ standard is 2,395 mm high inside and another’s is 2,390 mm, and published 40’ high cube reefer heights differ by just 1 mm. If a piece comes within about 5 cm of any limit, though, don’t rely on a table: ask the shipping line for the dimensions of the unit you will actually get, or have it checked.

What ISO 668 fixes, and what it doesn’t#

ISO 668 sets the external dimensions. Every 40’ container is 12.192 m long and 2.438 m (8 ft) wide, wherever it was built. A 20’ container is 6.058 m (19’10.5”) long and a 45’ is 13.716 m. Standard height is 2.591 m (8’6”), and a high cube is 2.896 m (9’6”).

Those outside measurements are fixed for a reason. Ship cell guides, the twistlocks on a truck chassis and crane spreaders all lock onto the same corner castings, so any container can move through any port and onto any truck. That interchangeability is what containerization has depended on for decades.

The inside is a different matter. Internal dimensions are what remains after the walls, corrugated panels, floor and door hardware take their share, and ISO 668 only sets minimums. For a 40’ standard container the minimum internal length is 11.998 m. Beyond that minimum, the inside is up to the manufacturer. In practice, a 40’ box that is 12.192 m long outside gives you about 12.03 m inside, some 16 cm less.

Weights are marked in two places, and they are not the same thing:

• CSC safety approval plate. CSC stands for the International Convention for Safe Containers. The CSC plate states the container’s maximum operating gross weight and the test loads for stacking and racking. It does not show the tare weight.
• Operational markings on the outside. Under ISO 6346, the maximum gross weight and the tare weight are painted on the container in letters at least 50 mm high, usually on the doors.

The marked tare weight matters for the Verified Gross Mass (VGM). There are two ways to get a VGM: weigh the packed container as a whole, or weigh all the cargo, packaging, pallets, dunnage and securing material and add the container’s tare weight. For that second method, the UK’s MCA guidance (MGN 534) tells shippers to use the tare weight indicated on the container, and it notes that tare weights of empty containers can differ slightly. So use the figure on the box, not a table average. The UK enforcement tolerance is ±5% or ±500 kg, whichever is greater. More on how these weights fit together in our guide to container weight limits and VGM.

How to read each column#

Door opening: the real limit for large pieces

On a dry container, the door opening is smaller than the inside. On carrier spec sheets for 20’ and 40’ standard containers, the door is 2,340 mm wide against an inside width of 2,350–2,352 mm, and 2,280–2,292 mm high against an inside height of 2,390–2,395 mm.

With the figures in our table, the door is 1 cm narrower than the inside (234 vs. 235 cm) and 11 cm lower (228 vs. 239 cm). On a high cube the height gap is 12.3 cm (257.7 vs. 270 cm). For any single large piece, the question is whether it gets through the door, not whether it fits inside.

Take a crate 232 cm tall. It would stand in a 40’ standard container with room to spare, since the inside height is 239 cm, but it can’t get past a 228 cm door. A piece 235 cm wide has the same problem: it matches the inside width but is 1 cm wider than the door. Cargo like this goes in an open top container, which has a removable roof and is loaded from above by crane, or on a flat rack, which has no side walls and can carry pieces wider or taller than the container itself. Both are quoted individually and usually cost extra.

High cube: the same floor, 30 cm more height

A 40’ high cube has exactly the same floor as a 40’ standard container. The only difference is height: 270 cm inside instead of 239 cm in our table, and 305 mm more in one shipping line’s published specs. That adds 8.6 m³ of capacity (76.3 vs. 67.7 m³), about 13% more.

The weight penalty is small. The tare weight goes from 3,700 kg to 3,880 kg, just 180 kg more.

Whether the extra height helps depends on your cargo. Light, bulky freight runs out of space before it reaches the weight limit, so more height means more cargo per box. Dense cargo reaches the weight limit before the space is full, and a taller box adds nothing.

Don’t assume a high cube always carries less weight. In our table its maximum payload is 28,620 kg, 180 kg below the 40’ standard’s 28,800 kg. One major line’s high cube carries 150 kg less than its standard box, while another line rates its high cube higher. Check the figure for the specific line and equipment.

Max payload: a structural limit, not a loading target

Maximum payload is the most the container can carry safely. It isn’t how much you can put on the road. A 20’ standard container is rated at about 28,200 kg; shipping lines publish figures such as 28,130 kg and 28,330 kg.

Load 28 t of cargo into a 40’ standard container and you are within its 28,800 kg payload, legal for the ocean leg. The truck is another story. On US Interstates the vehicle’s total weight is limited to 80,000 lb, with 20,000 lb on a single axle and 34,000 lb on a tandem, and that total has to cover the tractor, the chassis and the container’s tare weight as well as your cargo. In the EU, a three-axle tractor with a two- or three-axle semitrailer carrying a container in combined transport is capped at 44 t. The road leg can set the real limit, so check it before you book. The container weight limits guide covers this in more detail.

Reefer: less room than the dry equivalent

Compared with a 20’ standard container, a 20’ reefer gives up about 47 cm of length (590 vs. 542.5 cm), 6 cm of width (235 vs. 228.6 cm) and 13 cm of height (239 vs. 226.1 cm), and holds 28.0 m³ instead of 33.2 m³.

A 40’ high cube reefer loses 45 cm of length (1,203 vs. 1,158 cm), 6 cm of width (235 vs. 229 cm) and 20 cm of height (270 vs. 250 cm) against a 40’ high cube. Its tare weight is 740 kg higher (4,620 vs. 3,880 kg), and that comes out of your payload budget.

The space goes to the refrigeration unit at one end, the insulated walls and roof, and the T-floor (T-bar floor), whose ribbed channels let cold air flow under the cargo. On top of that, cargo has to stay below the max load line marked inside the container so air can circulate over it. The volume you can use is lower than the nominal capacity. For load lines, floor layout, pallet counts and power, see our reefer container dimensions guide.

What 30 cm of extra height is worth in boxes#

Take a box 60 × 40 × 40 cm, loaded upright so it stands 40 cm tall.

In a 40’ standard container, five layers use 200 cm of the 239 cm inside height and leave 39 cm empty above the cargo. A high cube’s 270 cm takes six layers (240 cm) with 30 cm to spare. Each layer on the 1,203 × 235 cm floor holds 100 boxes (20 along the length, 5 across the width), so the sixth layer is 100 more boxes.

Our Container Loading Calculator shows the same result. Enter 700 of these boxes at 8 kg each, more than either container can take, and it loads as many as fit:

• Boxes kept upright: 500 in the 40’ standard, 600 in the high cube, 20% more.
• Rotation allowed: 550 in the 40’ standard (78.1% of capacity) and 650 in the high cube (81.7%), about 18% more.

Run it yourself for the 40’ high cube and the 40’ standard container.

The gain depends entirely on box height. With 55 cm tall boxes, 239 cm fits four layers and so does 270 cm, because 270 ÷ 55 still rounds down to four. The high cube adds nothing. Extra height only pays off when it is enough to complete another layer.

That’s also why dividing total CBM by container capacity can mislead. The division counts every cubic meter, including the strip of height above the top layer that no box can use. A load simulation leaves that strip empty, as a real container would. If you only know your totals so far, start with the CBM Calculator: 500 of the same boxes at 8 kg come to 48 m³ and 4,000 kg, which it puts at two 20’ containers, one 40’ or one high cube. For how much of a container’s capacity you can realistically fill, see how many CBM fit in a container.

Five ways container dimensions get misread#

• Planning a 40’ as 40 feet inside. A crate built to the 12.19 m external length won’t fit in a 12.03 m interior. The cargo has to be repacked, the cut-off time (the deadline for delivering cargo to the terminal) is missed, and the shipment is delayed.
• Checking the inside but not the door. A piece that fits within 235 × 239 cm can still be stopped by a 234 × 228 cm door. By the time that’s discovered, the only options are an open top or a flat rack, quoted separately and at extra cost.
• Using dry figures for a reefer. Plan a 20’ reefer with a 20’ standard container’s 33.2 m³ when it really holds 28.0 m³, and on a volume basis about 16% of the order won’t fit.
• Loading to the number on the CSC plate. The maximum gross weight is a structural limit. Load to it and the truck can end up over the legal road limit, which means fines, part of the cargo moved to a second truck, and paying twice for the same leg.
• Trusting a table when the margin is tight. When a piece comes within about 5 cm of a limit, ask the shipping line for the dimensions of the actual container, or have it inspected.

Which container fits your cargo#

Most choices come down to one of four limits.

• Volume. As a rule of thumb, boxed cargo up to about 26 CBM suits a 20’ standard container, up to about 56 CBM a 40’ standard, and up to about 66 CBM a 40’ high cube. These are practical estimates, well below the nominal 33.2, 67.7 and 76.3 m³. Our guide to CBM per container explains why.
• Weight. Dense cargo reaches the weight limit before it fills the space. Splitting it across two 20’ containers can spread the load over more axles and keep each truck within road limits.
• Size of a single piece. If anything is larger than the 234 × 228 cm door opening of a standard container, look at an open top container or a flat rack.
• Quantity. For small shipments, LCL is often cheaper than a whole 20’ container. Where the break-even falls depends on rates, with roughly 13–15 CBM a common rule of thumb, so compare both in our FCL vs. LCL guide before you book a full container load (FCL).

To check a specific box in a specific container, including whether you’ll run out of space or weight first, use the Container Loading Calculator.