| HO (H0) | |
|---|---|
 HO scale (1:87) model of a center cab switcher locomotive made by Bachmann, shown with a pencil for size comparison. | |
| Scale | 3.5 mm to 1 ft (305 mm) |
| Scale ratio |
|
| Standard(s) | |
| Model gauge | 16.5 mm (0.65 in) |
| Prototype gauge | Standard gauge |
HO or H0 is a rail transport modelling scale using a 1:87 scale (3.5 mm to 1 foot). It is the most popular scale of model railway in the world.[1][2] The rails are spaced 16.5 millimetres (0.650 in) apart for modelling 1,435 mm (4 ft 8+1⁄2 in) standard gauge tracks and trains in HO.[3]
The name HO comes from 1:87 scale being half that of O scale, which was originally the smallest of the series of older and larger 0, 1, 2 and 3 gauges introduced by Märklin around 1900. Rather than referring to the scale as "half-zero" or "H-zero", English-speakers have consistently pronounced it /eɪtʃ oʊ/ and have generally written it with the letters HO. In other languages it also remains written with the letter H and number 0 (zero); in German it is thus pronounced as [ha: 'nʊl]. In Japan, many models are produced using 1:80 scale proportions (16.5mm track is still used).
- ^ "Guide to model railroading scales and gauges". Model Railroader. 2 November 2011. Archived from the original on 22 June 2015. Retrieved 2 October 2016.
- ^ Johnson, Kent J., ed. (1998). Basic Model Railroading: Getting Started in the Hobby. Kalmbach Publishing, Co. p. 6. ISBN 978-0-89024-334-3. Retrieved 24 October 2017.
- ^ "Modeling Scales: Scale and Gauge". NMRA. 26 December 2000. Archived from the original on 15 March 2010. Retrieved 4 March 2010.