About this calculator
On a container door, usually just below the container number, you will find a four-character code such as 22G1 or 45G1. This is the ISO 6346 size-type code. The same code appears in carrier EDI messages, terminal reports and sometimes on the Bill of Lading, so export staff, forwarders and truck drivers often need to confirm that the box released by the depot matches the one that was booked.
The structure: the first character gives the outside length (2 = 20 ft, 4 = 40 ft, L = 45 ft), the second gives the outside height and width (2 = 8'6", 5 = 9'6" high cube; letters such as C, E or N mark boxes wider than 2,438 mm), and the third and fourth give the type and its detail, for example G1 for a general-purpose box with passive vents, R1 for a reefer that can both cool and heat, U1 for an open top, P1 or P3 for a flat rack and T for a tank container.
This calculator breaks down each character using the ISO 6346 code tables (1995 edition) and shows the length in mm and feet, the height, the width class, the type group (GP, RT, UT, PF, TD and others) and a plain-language explanation. Old all-numeric codes from before 1995, such as 2210 or 4510, are decoded for size only. Codes it does not recognise are flagged so you can re-check what is painted on the box. For exact inside dimensions, still check the unit's own markings or the owner's specification sheet.
Worked example
Decoding 22G1 and 45G1:
- 22G1: first character 2 = 20 ft long (6,058 mm)
- 22G1: second character 2 = 8'6" high (2,591 mm), standard 2,438 mm width
- 22G1: type G1 = general purpose (dry) with passive vents at the top, group GP
- 45G1: 4 = 40 ft (12,192 mm), 5 = 9'6" (2,896 mm, high cube), G1 = dry
- For comparison: 45R1 = same size, refrigerated and heated reefer (group RT); L5G1 = 45 ft (13,716 mm) high cube dry
So 22G1 is a standard 20' dry box and 45G1 is a 40' High Cube dry box.
How to use it
Find the code on the door
Look for the 4-character code on the container door, usually below the container number, for example 22G1 or 45R1.
Type the code
Enter the four characters. Lower case and spaces are handled automatically.
Read the breakdown
See what each character means: length, height and width, type group, and details such as ventilation or tank test pressure.