Guide
OO vs N vs TT:120
The scale you pick decides how much railway fits in your room, what you can buy ready-to-run, and how fiddly it is to handle. Here’s how to choose.
The quick answer
- OO if you want the biggest choice of British models, easy handling and the most second-hand bargains.
- N if space is tight or you love long trains running through scenery.
- TT:120 if you want something in between and are happy with a newer, growing range (mainly from Hornby).
Side-by-side comparison
| OO | TT:120 | N | |
|---|---|---|---|
| Scale | 1:76.2 (4mm to the foot) | 1:120 | 1:148 (UK) |
| Track gauge | 16.5mm | 12mm | 9mm |
| Space for a basic oval | About a 1.6m × 1.1m board | Noticeably smaller than OO | Roughly a quarter of the OO area |
| UK ready-to-run choice | Huge | Growing | Large |
| Handling & eyesight | Easiest | Moderate | Fiddly |
| Second-hand market | Very large | Small (new scale) | Large |
OO gauge
OO is the default British scale. Hornby, Bachmann, Accurascale, Dapol, Heljan and others make a vast range of British locomotives and rolling stock, and Peco and Hornby track is everywhere. Models are big enough to handle easily, couple up and re-rail without tweezers, and to fit sound decoders with decent speakers.
The catch is space. Even a simple oval with a couple of sidings wants a board of around 1.6m by 1.1m, and realistic main-line trains look best on long, gentle curves that need a spare room, loft or garage.
N gauge
N gauge is roughly half the size of OO. In the UK it’s 1:148 scale running on 9mm track, with Graham Farish (Bachmann), Dapol, Revolution and others producing British outline models. The big advantage is space: a full-length express or a long freight train actually looks right on a layout that fits along one wall.
It is fiddlier to handle, couplings are smaller, and track cleanliness matters more. But scenery goes a long way, and you can build a convincing landscape in a modest room.
TT:120
TT:120 (1:120 on 12mm track) has been popular in continental Europe for decades; Hornby launched a British TT:120 range in 2022, and other makers have followed. It sits neatly between OO and N: detailed enough to enjoy close up, small enough to fit more railway on a table top.
Because the British range is newer, there’s less choice and far fewer second-hand bargains than in OO or N. If the models you love are already available, it’s a very attractive option.
O gauge and HO
O gauge (7mm to the foot, 32mm track) is large and impressive, and suits garden railways or a long shelf in a shed. It costs more per model and needs a lot of space. HO (1:87) uses the same 16.5mm track as OO but at a slightly smaller scale; it’s the world standard for continental and American models. HO and OO trains run on the same track, but look mismatched side by side.
How to decide
- Measure your space. Be honest about the board you can fit, and whether you can reach the middle (about 60cm reach is comfortable).
- List five trains you’d love to own. Check which scales they’re made in ready-to-run.
- Think about who’s using it. Younger children and anyone with less steady hands will find OO much easier.
- Look at budget. N and TT:120 locomotives aren’t much cheaper than OO, but you need less baseboard. OO’s second-hand market can stretch a budget furthest.