There are many scales to choose from, here is a NEM list published by MOROP:
OO is a separate UK standard, that is very popular but has 4mm to 1 foot for standard gauge. There are a large number of new and second hand engines and rolling stock available in this scale.
- no letter = standard gauge (prototype: 1,250–1,700 mm or 49.2–66.9 in)
- m = metre gauge (prototype: 850–1,250 mm or 33.5–49.2 in)
- e = narrow gauge (prototype: 650–850 mm or 25.6–33.5 in)
- i = industrial (prototype: 400–650 mm or 15.7–25.6 in)
- p = park railway (prototype: 300–400 mm or 11.8–15.7 in)
| Scale | Ratio | Standard gauge | m | e | i | p | Notes |
|---|---|---|---|---|---|---|---|
| T | 1:480 | 3 mm (0.118 in) | – | – | – | T gauge; the scale ratio of 1:450 in the UK. | |
| Z | 1:220 | 6.5 mm (0.256 in) | 4.5 mm | – | – | – | Based on Märklin factory standards. |
| N | 1:160 | 9 mm (0.354 in) | 6.5 mm | 4.5 mm | – | – | Based on Arnold factory standards. |
| TT | 1:120 | 12 mm (0.472 in) | 9 mm | 6.5 mm | 4.5 mm | – | – |
| H0 | 1:87 | 16.5 mm (0.65 in) | 12 mm | 9 mm | 6.5 mm | 4.5 mm | “Half O” |
| S | 1:64 | 22.5 mm (0.886 in) | 16.5 mm | 12 mm | 9 mm | 6.5 mm | – |
| 0 | 1:45 | 32 mm (1.26 in) | 22.5 mm | 16.5 mm | 12 mm | 9 mm | |
| 1 | 1:32 | 45 mm (1.772 in) | 32 mm | 22.5 mm | 16.5 mm | 12 mm | – |
| II | 1:22.5 | 64 mm (2 1⁄2 in) | 45 mm | 32 mm | 22.5 mm | 16.5 mm | Known as Gauge 3 in the UK; |
| III | 1:16 | 89 mm (3 1⁄2 in) | 63.5 mm | 45 mm | 32 mm | 22.5 mm | – |
| V | 1:11 | 5 in (127 mm) | 89 mm | 63.5 mm | 45 mm | 32 mm | – |
| VII | 1:8 | 184 mm (7 1⁄4 in) | 127 mm | 89 mm | 63.5 mm | 45 mm | – |
| X | 1:5.5 | 260 mm (10 1⁄4 in) | 184 mm | 127 mm | 89 mm | 63.5 mm | – |