OOG (out of gauge) is sea cargo whose dimensions exceed the external limits of a standard container and which is therefore carried on a flat rack, open top or platform container. Depending on the direction of the overhang, it is defined as over height (OH), over width (OW) or over length (OL). Because it makes neighbouring container slots on the vessel unusable, it is priced with additional freight.
What determines OOG dimensions?
Container ships and terminals are built around the dimensions in the ISO 668 standard. A standard container has an external width of 2.438 m and a height of 2.591 m; in the high cube type the height rises to 2.896 m. A 20 ft container is 6.058 m long and a 40 ft container 12.192 m. Cell guides in the holds, the stowage pattern and crane spreaders all work around this box. If the cargo protrudes beyond this external envelope in any direction, it counts as OOG. The family of dimensions is detailed in the entry on container types and dimensions.
| Abbreviation | Meaning | Example |
|---|---|---|
| OH (Over Height) | The cargo exceeds the upper limit of the container | A machine body protruding above an open top |
| OW (Over Width) | The cargo overhangs at the sides; left and right overhang are measured separately | A tank with a diameter of 3.2 m |
| OL (Over Length) | The cargo overhangs at the front or rear end | A long pipe bundle, a steel girder |
What equipment is it carried on?
- Flat rack: A container without side walls or roof, with collapsible end walls. Most OW and OH cargo is carried on one (see flat rack container).
- Open top: A container with a tarpaulin roof; preferred when the cargo protrudes only at the top or needs to be loaded from above by crane (when to use an open top).
- Platform: A flat base without end walls. Several flat racks or platforms can be placed side by side to create a deck for wider cargo.
If the cargo exceeds even the limits of these arrangements, the container system is abandoned and the cargo is loaded directly into the ship's hold or onto its deck as breakbulk.
Why is additional freight charged?
The main cost is the lost slot. Cargo protruding at the top prevents containers from being stacked on it. Cargo overhanging at the sides makes neighbouring slots unusable. The line passes on the revenue of these empty slots as an OOG surcharge; the surcharge varies with the amount of overhang. OOG cargo is usually stowed in the top tier on deck or in a place where nothing will be stacked on top of it. For this reason, the OOG capacity of a vessel is limited, and the booking should be approved early, together with dimensions and drawings.
On the terminal side, a standard spreader cannot be used either; the cargo is handled with a special lifting frame or slings, and this service is charged separately.
How it relates to the oversize concept on the road
The two concepts often appear together but are not the same. OOG is a maritime term that takes its dimensions from the container standard. Oversize cargo, on the other hand, is defined by the 2.55 m width and 4.00 m height limits in Türkiye's Highway Traffic Regulation (Karayolları Trafik Yönetmeliği).
- A machine 2.50 m wide counts as OW on a flat rack because it exceeds 2.438 m. The same machine does not need a permit on the road because it stays within the 2.55 m limit.
- The reverse also happens: a flat rack base is about 0.6 m thick. A load 2.4 m high is OH on the ship, and since the total height on a container chassis may exceed 4 m, it may also require a special permit on the road leg.
This is why the container transport leg between the port and the factory should be planned at the same time as the sea booking.
Common mistakes
- Giving the overhang as a single total width; the line asks for left and right overhang separately, in centimetres.
- Not including chocks, crates and lashing elements in the dimensions.
- Finding out after booking that the transhipment port or feeder vessel does not accept OOG.
- Requesting flat rack loading without providing centre of gravity information; the lashing plan is based on this data.