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Container ISO size and type codes: 22G1, 42G1, 45G1, 45R1 explained

Besides the container number, ISO 6346 sets a 4-character size and type code marked on each container. The first character is the length, the second the height, and the last two the type: 22G1 is a standard 20 ft general purpose box, 42G1 a standard 40 ft and 45G1 a 40 ft high cube.

Checked against official sources: 2026-10

At a glance

StandardISO 6346, Freight containers – Coding, identification and marking
1st character: length2 = 20 ft (6,096 mm), 4 = 40 ft (12,192 mm), L = 45 ft (13,716 mm)
2nd character: height0 = 8 ft (2,438 mm), 2 = 8 ft 6 in (2,591 mm), 5 = 9 ft 6 in (2,896 mm), the high cube
3rd and 4th: typeG general purpose, R reefer, U open top, P platform or flat rack, T tank, B bulk, V ventilated, H thermal
22G1 / 42G120 ft and 40 ft standard-height general purpose containers
45G1 / 45R140 ft high cube general purpose and 40 ft high cube reefer
L5G145 ft high cube general purpose container
Container number3-letter owner code, equipment category (U, J or Z), 6-digit serial number and a check digit

Common size and type codes

How to read the type characters

The third character gives the type group: G for general purpose, R for refrigerated, U for open top, P for platforms and flat racks, T for tanks, B for bulk, V for ventilated and H for thermal containers. The fourth character gives the detail within the group. G1, for example, is a general container with passive vents, R1 a mechanically refrigerated and heated container, U1 an open top with removable top members, P1 a platform with fixed ends and T1 a tank for non-dangerous liquids.

The width is normally 8 ft (2,438 mm), so the second character mostly signals height. A 2 in that position means the standard 8 ft 6 in box and a 5 means a high cube of 9 ft 6 in, which is why the same 40 ft length appears as 42G1 or 45G1.

Container numbers and the BIC owner code

The container number is built from a 3-letter owner or operator code, a fourth letter for the equipment category (U for freight containers, J for detachable container-related equipment, Z for trailers and chassis), a 6-digit serial number and a check digit that validates the rest. The Bureau International des Containers (BIC) has kept the register of owner codes since 1970, and ISO adopted the system in 1972; only owner codes registered with BIC may be used to identify containers in international transport and customs documents.

Step by step

  1. Read the 4-character code printed next to the container number.
  2. Check the first character for length: 2 for 20 ft, 4 for 40 ft, L for 45 ft.
  3. Check the second character for height: 2 for standard, 5 for high cube.
  4. Check the type: G general purpose, R reefer, U open top, P flat rack, T tank.
  5. Make sure the booking, packing list and bill of lading show the same container type.
  6. Verify the container number's check digit before you send documents.

Documents you usually need

Common problems and how to avoid them

The booking says 40 ft high cube but a 42G1 was delivered.

What to do: 42G1 is a standard-height 40 ft; a high cube is 45G1. Ask the carrier to swap it before loading.

A 45G1 is read as a 45 ft container.

What to do: The first character 4 means 40 ft and the 5 means 9 ft 6 in high; a 45 ft container starts with L, as in L5G1.

A container number is rejected by a system.

What to do: Check the owner code, the category letter, the 6-digit serial and the check digit; a single wrong character changes the check digit.

Cargo for a reefer was booked as a general purpose container.

What to do: Reefers use R type codes such as 22R1 or 45R1; correct the booking before the empty is released.

Sources

  1. The international register of container owner codes (BIC codes) Bureau International des Containers
  2. Common ISO container size and type codes (2022) The Geography of Transport Systems
  3. ISO 6346 Wikipedia

Rules change often. This note is practical guidance based on the sources above, not legal advice. Confirm current requirements with the authority, your importer or a licensed customs broker before you ship.

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Common questions

What does 22G1 mean on a container?

A 20 ft general purpose container with a standard height of 8 ft 6 in.

What is the difference between 42G1 and 45G1?

Both are 40 ft general purpose containers; 42G1 is 8 ft 6 in high and 45G1 is a 9 ft 6 in high cube.

What does 45R1 mean?

A 40 ft high cube reefer: mechanically refrigerated and heated.

How is a 45 ft container coded?

With L as the first character, for example L5G1 for a 45 ft high cube general purpose container.

What is the U in a container number?

The equipment category: U is for freight containers, J for detachable container-related equipment and Z for trailers and chassis.

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