Gauge
HO scale has several gauges representing both standard and narrow gauges in roughly 1:87 scale. Standards are defined by the NMRA (in North America) and the NEM (in Continental Europe). While the standards are in practice interchangeable, they are not strictly identical.
| Track gauge | Names | Prototype | Notes |
|---|---|---|---|
| 16.5 mm (0.650 in) | HO (NMRA) and H0 (NEM) | Standard gauge | 16.5 mm (0.650 in) track is also used for British OO gauge |
| 12 mm (0.472 in) | HOn3½ (NMRA) and H0m (NEM) | Metre gauge and 3 ft 6 in (1,067 mm) (Cape gauge) |
Metre gauge is used in west and east Africa, parts of other countries and many tram lines. Cape gauge is used in southern Africa, Queensland (Aus), New Zealand and also non-Shinkansen JR lines in Japan. H0m and HOn3½ use commercially available TT scale track. |
| 10.5 mm (0.413 in) | HOn3 (NMRA) | 3 ft (914 mm) gauge | 3 ft (914 mm) gauge once common to American mining railroads and shortlines, particularly in the Western States |
| 9 mm (0.354 in) | HOn30 (NMRA) and H0e (NEM) | 2 ft 6 in (762 mm) gauge | Typically used for lines in 2 ft (610 mm)-2 ft 6 in (762 mm) gauge. Uses commercially available N scale track. |
| 6.5 mm (0.256 in) | HOz (NMRA) and H0i (NEM) | 15 in (381 mm) gauge | Uses commercially available Z scale track. |
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