What does 22G1 or 45G1 on a container mean?

It is the ISO 6346 size and type code. The first character is the length (2 = 20 ft, 4 = 40 ft, L = 45 ft), the second the height and width (2 = 8 ft 6 in, 5 = 9 ft 6 in high cube), the last two the type (G1 = general purpose with vents, R1 = reefer, U1 = open top, P3 = flatrack).

The CSC Safety Approval Plate shows that the container is approved under the 1972 International Convention for Safe Containers. It lists the approval reference, date of manufacture, maximum gross mass, allowable stacking load and racking test force, plus the next examination date or an ACEP reference. A box without a valid plate should not move in international transport.

What is the difference between max gross, tare and payload?

Max gross is the most the loaded box may weigh. Tare is the empty box. Payload (net) is max gross minus tare, the most cargo you can load. Road and rail limits on the inland leg are often lower than the box rating.

What does ACEP mean on a container?

Approved Continuous Examination Programme. The owner inspects the box at every major repair, refurbishment or on-hire/off-hire interchange under a scheme approved by an Administration, instead of fixed-date examinations. The plate then shows ACEP and the programme reference instead of a next examination date.

Container Markings.

What is painted on the doors of a shipping container and what the CSC plate says. Codes follow ISO 6346, the plate follows the 1972 Convention for Safe Containers.

What is on the door

A typical 40' high cube door. Numbers on the drawing match the list.

Container number: owner code, serial and check digit, top right and on every side and roof. How to read it
Size and type code: four characters under the number. Code table
Weights: max gross, tare, net (payload) and cubic capacity. What they mean
CSC plate: safety approval, often next to the customs (TIR) and manufacturer plates. Every line
High cube stripes: yellow and black marks on boxes taller than 8 ft 6 in. Other marks

The container number

Eleven characters, unique worldwide. Example: MSKU 029724 0.

Part	Example	Meaning
Owner code	`MSK`	Three letters registered with the BIC. Belongs to the owner or main operator, often a leasing company rather than the line.
Equipment category	`U`	U freight container, J detachable equipment (for example a clip-on genset), Z trailer or chassis.
Serial number	`029724`	Six digits chosen by the owner.
Check digit	`0`	Calculated from the first ten characters. Usually printed in a box. A wrong digit means a typo.

Check any number and find the line behind a prefix with the container number decoder.

Size and type code

Four characters: length, height and width, then type and detail. 45G1 reads as 40 ft long, 9 ft 6 in high, general purpose with vents.

1st character: length

Code	Length
`1`	10 ft (2,991 mm)
`2`	20 ft (6,058 mm)
`3`	30 ft (9,125 mm)
`4`	40 ft (12,192 mm)
`L`	45 ft (13,716 mm)
`5`	45 ft (2022 edition) (13,716 mm)
`B`	24 ft
`C`	24 ft 6 in
`G`	41 ft
`H`	43 ft
`M`	48 ft
`N`	49 ft

2nd character: height and width

Code	Height	Width
`0`	8 ft (2,438 mm)	2,438 mm
`2`	8 ft 6 in (2,591 mm)	2,438 mm
`4`	9 ft (2,743 mm)	2,438 mm
`5`	9 ft 6 in (2,896 mm)	2,438 mm
`6`	over 9 ft 6 in	2,438 mm
`8`	4 ft 3 in (1,295 mm)	2,438 mm
`9`	up to 4 ft (1,219 mm)	2,438 mm
`C`	8 ft 6 in	2,438 to 2,500 mm (pallet wide)
`D`	9 ft	2,438 to 2,500 mm (pallet wide)
`E`	9 ft 6 in	2,438 to 2,500 mm (pallet wide)
`F`	over 9 ft 6 in	2,438 to 2,500 mm (pallet wide)
`L`	8 ft 6 in	over 2,500 mm
`M`	9 ft	over 2,500 mm
`N`	9 ft 6 in	over 2,500 mm
`P`	over 9 ft 6 in	over 2,500 mm

3rd and 4th characters: type

Code	Type	Group	4th character	Container types
`G`	General purpose (dry)	GP	G0 doors at one or both ends; G1 also passive vents at the top; G2/G3 full or partial side openings.	Dry containers
`V`	Ventilated	VH	V0 passive vents low and high; V2 and V4 mechanical ventilation inside or outside.	–
`B`	Dry bulk	BU / BK	Non-pressurised (B0 to B2) or pressurised discharge (B3 to B6), with loading hatches in the roof.	Bulk
`S`	Named cargo	SN	Built for one cargo: livestock, cars, live fish.	–
`R`	Reefer (integral unit)	RE / RT / RS	R0 cooling only; R1 cooling and heating (the usual reefer, 22R1, 45R1); R2/R3 self-powered.	Reefers
`H`	Insulated, or reefer with removable unit	HR / HI	H0 to H2 clip-on or porthole units; H5/H6 insulated only.	–
`U`	Open top	UT	U0 open roof; U1 also removable header at the door end; higher numbers add side openings or a hard top.	Open tops, Hardtops (U6)
`P`	Platform, flatrack	PL / PF / PC / PS	P0 platform; P1/P2 fixed ends; P3/P4 folding ends (most flatracks are 22P3 or 45P3); P5 open-sided superstructure.	Flatracks, Platforms
`T`	Tank	TN / TD / TG	T0 to T2 non-dangerous liquids; T3 to T6 dangerous liquids; T7 to T9 gases. The digit steps up with test pressure.	Tanks
`A`	Air/surface	AS	Intermodal boxes that also fit aircraft holds.	–

Common codes

22G0 22G1 42G0 42G1 45G0 45G1 L5G0 L5G1 22U6 42U6 22U1 42U1 45U1 22P3 45P3 29P0 49P0 22B0 22R1 22R9 45R1 45R9

45 ft is coded L in the 1995 edition and 5 in the 2022 edition. Boxes in service mostly carry L5G1 for a 45' high cube.
Older boxes can carry the pre-1995 code (for example 4510 or 2210). Carriers' EDI systems map both.
Sources: ISO 6346, BIC size and type code. Full tables are in the standard.

Weights and capacity

Mark	Meaning
`MAX GROSS`	Most the loaded box may weigh, in kg and lb. Same as the maximum operating gross mass on the CSC plate. 30,480 kg on older boxes, 32,500 to 36,000 kg on newer ones.
`TARE`	Weight of the empty box with its fixed fittings. Used to compute VGM by method 2.
`NET` / `PAYLOAD`	Max gross minus tare: the most cargo you can load.
`CU.CAP.`	Inside volume in cubic metres and cubic feet.

Figures for each box type: Container Types. Road and rail limits on the inland leg are often lower than the box rating.

CSC Safety Approval Plate

Required on every container in international transport by the International Convention for Safe Containers (IMO, 1972). It proves the design passed lifting, stacking and racking tests.

CSC SAFETY APPROVALThe heading. The plate is permanently fixed at a readily visible place, usually on the left door.

Approval referenceCountry of approval and the approval number given by that Administration or a class society acting for it (BV, DNV, LR, ABS, CCS and others).

Date manufacturedMonth and year of manufacture.

Identification No.The manufacturer's serial for the box. This is not the container number painted on the doors.

Maximum operating gross massBox plus cargo, in kg and lb. The same figure as MAX GROSS on the door.

Allowable stacking load for 1.8 gWeight the box can carry on top of it at sea. 192,000 kg is a common rating on modern dry boxes.

Transverse racking test forceSideways force the end frames passed in the test, in newtons.

End wall / side wall strengthShown only when it differs from the standard 0.4 P (end) and 0.6 P (side) of payload.

Next examination or ACEPEither the date of the next examination (periodic scheme: first within 5 years of manufacture, then at most every 30 months) or an ACEP reference, meaning the owner runs an approved continuous examination programme.

Plate values are an example. Content per CSC Annex I, Regulation 1; examination rules per Regulation 2.

The plate is metal, fixed for the life of the box. Data plates for customs (TIR, CCC) and the manufacturer often sit next to it.
A missing, unreadable or expired plate is a reason for a terminal or authority to stop the box.
The CSC applies to boxes with corner fittings and a base of at least 14 m² (7 m² with top corner fittings). Air containers are out of scope.

Other marks you will see

Mark	Meaning
Yellow and black chevrons	Height warning for boxes over 2.6 m (8 ft 6 in), on the top corners. A high cube sign ("9'6"" or "HC") is often painted too.
Country code	Optional two-letter country code of the owner (ISO 3166). Rare on new boxes.
Electrical warning	Overhead line warning on the ladders and corner posts of boxes with access steps.
Reduced strength letter	A letter in the 4th position of the size-type code marks a box with reduced stacking or racking strength. Stow it accordingly.
IMO placards	Dangerous goods labels on all four sides. See the class on the booking.
Floor and timber treatment	Australian quarantine plate (wooden floor treatment) on the door of many boxes.

FAQ

What does 22G1 or 45G1 on a container mean? It is the ISO 6346 size and type code. The first character is the length (2 = 20 ft, 4 = 40 ft, L = 45 ft), the second the height and width (2 = 8 ft 6 in, 5 = 9 ft 6 in high cube), the last two the type (G1 = general purpose with vents, R1 = reefer, U1 = open top, P3 = flatrack).
What is a CSC plate? The CSC Safety Approval Plate shows that the container is approved under the 1972 International Convention for Safe Containers. It lists the approval reference, date of manufacture, maximum gross mass, allowable stacking load and racking test force, plus the next examination date or an ACEP reference. A box without a valid plate should not move in international transport.
What is the difference between max gross, tare and payload? Max gross is the most the loaded box may weigh. Tare is the empty box. Payload (net) is max gross minus tare, the most cargo you can load. Road and rail limits on the inland leg are often lower than the box rating.
What does ACEP mean on a container? Approved Continuous Examination Programme. The owner inspects the box at every major repair, refurbishment or on-hire/off-hire interchange under a scheme approved by an Administration, instead of fixed-date examinations. The plate then shows ACEP and the programme reference instead of a next examination date.