Shipping Container Specifications & Dimensions

Internal dimensions vs. door opening: why the door decides what fits

The door frame is narrower and lower than the inside of the box. On 20ft and 40ft standard containers, carriers list a door opening 2,340 mm wide against an inside width of 2,350–2,352 mm. That's only about 1 cm less in total, or roughly half a centimeter on each side. Height is where the door really costs you: 2,280–2,292 mm at the door versus 2,390–2,395 mm inside, a loss of about 10.3–11 cm to the door header.

The table above shows the same pattern. Every dry type loses 1 cm of width at the door; the 20ft and 40ft standard lose 11 cm of height, and the high cubes lose 12.3 cm.

So a crate or machine that clears the internal height on paper can still catch on the header. Measure tall items against the door height, not the inside height. Reefers are the exception on width: the door is as wide as the inside or slightly wider (229 cm door vs 228.6 cm inside on the 20ft reefer in the table; Hapag-Lloyd lists 2,290 mm vs 2,280 mm). In a reefer it's the insulated side walls, not the door, that set the width limit.

20ft, 40ft, 40ft high cube or 45ft: which size to book

A 40ft standard container holds 67.7 m³ against 33.2 m³ for a 20ft, about 2.04 times the space. The inside length roughly doubles (1,203 cm vs 590 cm) while width and height stay the same.

The 40ft high cube has the same floor as the 40ft standard but stands one foot taller outside: 9'6" instead of 8'6" (2.896 m vs 2.591 m). Inside, that adds 305 mm of height and about 8.6 m³ of volume (76.3 m³ vs 67.7 m³). The 45ft high cube adds length instead of height: 1,355 cm inside versus 1,203 cm for the 40ft high cube (152 cm more), and 86.1 m³ versus 76.3 m³ (9.8 m³ more), with the same 270 cm inside height.

The right size depends on what runs out first. Light, bulky cargo runs out of space before reaching the weight limit, so the extra height of a high cube or the extra length of a 45ft pays off. Dense cargo reaches the weight limit before the space is full, and a bigger box only adds room you can't use. For heavy loads, check the payload column and the road limits below before moving up a size.

Payload, road weight limits and VGM

Payload is the maximum gross weight minus the tare weight. Hapag-Lloyd's 20ft standard container, for example, has a 30,480 kg max gross and a 2,350 kg tare, which leaves a 28,130 kg max payload.

The max gross rating isn't the same on every box. A 40ft container may be rated at 30,480 kg or 32,500 kg depending on the carrier and the equipment, so two 40ft units can have quite different payloads. ISO 668 has allowed up to 36,000 kg since its 2016 amendment (the earlier cap was 30,480 kg), but what counts is the rating on the unit you're actually given.

The truck leg has its own limits, and they often stop you before the container's payload does. On the US Interstate system, a vehicle's gross weight is capped at 80,000 lb, with 20,000 lb on a single axle and 34,000 lb on a tandem, and the tractor, chassis and empty container all count toward that total. Under the EU rules for international road transport, a three-axle tractor pulling a semi-trailer with an intermodal container is limited to 44 t. Road rules differ by country, so confirm the limits for your route with the trucking company before planning a heavy load.

Verified Gross Mass (VGM) is a declaration requirement, not a weight limit. Under SOLAS chapter VI, regulation 2, in force since July 1, 2016, the shipper must submit a verified gross mass before the container can be loaded onto the ship. There are two ways to get it. Method 1: weigh the packed container on calibrated, certified equipment. Method 2: weigh all the cargo, packaging, pallets, dunnage (loose material used to support and protect cargo) and securing material, and add the container's tare weight. Method 2 must follow a certified method approved in the country where the container is packed; in the UK, that approval comes from the Maritime and Coastguard Agency (MCA). UK enforcement allows a tolerance of ±5% or ±500 kg, whichever is greater.

Reefer, open top and flat rack: when a standard box won't work

Reefer containers (refrigerated containers) carry temperature-controlled cargo. The refrigeration unit sits at one end and the walls are insulated, so a reefer is smaller inside and heavier than a dry container of the same length. Cargo has to stay below the max load line, the marked limit on how high cargo can be stowed, and the T-floor (T-bar floor, the grooved rails that let cold air circulate under the load) has to be left clear. The usable volume is therefore less than the nominal figure.

An open top container has no fixed roof. Removable roof bows and a tarpaulin cover the top, so heavy or bulky cargo can be lowered in by crane. In the table, the 20ft and 40ft open tops have the same 234.8 cm inside height and 234 × 228 cm door opening. Hapag-Lloyd and ONE list their 40ft open-top containers at 4,050 kg and 3,880 kg tare, with 28,450 kg and 26,600 kg payload.

A flat rack has no side walls. It's built for heavy or bulky cargo and for pieces that are over-height or over-width, and models with collapsible end walls can also take cargo longer than the container. The flat rack rows in the table use CMA CGM's figures: a 20ft flat rack at 34,000 kg max gross, 2,750 kg tare and 31,250 kg payload, and a 40ft at 52,500 kg, 5,100 kg and 47,400 kg.

Out-of-gauge (OOG) cargo, meaning oversized cargo that exceeds the container's dimensions, is quoted separately and can come with surcharges and extra securing requirements. Give your freight forwarder or carrier the actual piece dimensions and weight when you ask for a rate.

Reefer container dimensions and weight: 20ft vs. 40ft high cube

In the table, the 20ft reefer measures 542.5 × 228.6 × 226.1 cm inside, with 28.0 m³ of capacity, a 3,080 kg tare weight and a 27,400 kg payload. The 40ft high cube reefer (40RH) measures 1,158 × 229 × 250 cm, with 67.0 m³, a 4,620 kg tare and a 29,380 kg payload. A 40ft reefer is normally a high cube unit; CMA CGM's reefer fleet, for example, is made up of 20ft, 40ft high cube and 45ft boxes.

Compared with a dry container of the same length, a reefer is several hundred kilograms heavier: 800 kg more for the 20ft and 740 kg more against the 40ft high cube in this table, and 510–790 kg more when you compare units from the same carrier. It's also about 6–6.4 cm narrower inside (228.6 cm or 229 cm vs 235 cm), which leaves less slack when you place pallets side by side.

The space you can actually fill is smaller again. CMA CGM quotes its 20ft reefer at 28.6 m³ nominal but 27.3 m³ in use, with 2,158 mm of height usable for cargo; its 40ft high cube reefer is 68 m³ nominal, 64.9 m³ in use, with 2,394 mm usable height.

Tare weights vary by carrier as well. Hapag-Lloyd and ONE list 2,860 kg and 2,810 kg for a 20ft reefer, and 4,420 kg and 4,490 kg for a 40ft high cube reefer rated at 34,000 kg max gross. CMA CGM's averages are 3,010 kg and 4,700 kg.

Common mistakes when reading container specs

Taking the nominal size as the inside size: 20ft, 40ft and 45ft are external lengths (6.058 m, 12.192 m and 13.716 m). Every type is 8 ft (2.438 m) wide outside, standard boxes are 8'6" high and high cubes are 9'6". The internal dimensions are always smaller. ISO 668 only sets minimums (for example, an inside length of 11.998 m for a 40ft), and actual figures vary by manufacturer.

Assuming every box has the same tare weight: the same 20ft standard container weighs 2,350 kg at one carrier and 2,150 kg at another, and CMA CGM gives an average of 2,230 kg. If you declare VGM by Method 2, use the tare marked on the actual unit, not a figure from a table.

Looking for the tare on the CSC plate: the CSC safety approval plate is permanently fixed in a readily visible place, usually riveted to the outside of the left-hand door. It shows "CSC SAFETY APPROVAL", the approving country and approval number, the month and year of manufacture, the manufacturer's identification number, the maximum operating gross mass in kg and lb, the allowable stacking load for 1.8 g and the transverse racking test load. It doesn't show the tare weight.

The tare is part of the ISO 6346 markings painted on the doors, in characters at least 50 mm high, along with the max gross, which matches the figure on the CSC plate. Some owners add the payload as well.