| Gauge 1 | |
|---|---|
 Gauge 1 model of a Ruston & Hornsby locomotive | |
| Scale | 3⁄8 in (9.5 mm) to 1 ft (305 mm) |
| Scale ratio | ca. 1:32 |
| Model gauge | 1.75 in (44.45 mm) |
| Prototype gauge | 4 ft 8+1⁄2 in (1,435 mm) standard gauge |
1 gauge, gauge 1 or gauge one is a model railway and toy train standard that was popular in the early 20th century, particularly with European manufacturers. Its track measures 1.75 in (44.45 mm), making it larger than 0 gauge but slightly smaller than wide gauge, which came to be the dominant U.S. standard during the 1920s.
Gauge one was standardised, according to Model Railways and Locomotive magazine of August 1909, at 1.75 in (44.45 mm). An exact 1:32 scale would yield 1.766 in (44.85 mm) for standard gauge prototype. The distance between the wheel tyres was set at 1+17⁄32 in (38.894 mm) and between the centre of the track 48 mm (no inch equivalent suggesting it was metric users' requirement only). The wheel width was set at 19⁄64 in (7.541 mm).
Definitions using gauge, rather than scale, were more common in the early days with the four gauges for which standards were adopted being No. 0 (commonly called O gauge currently), No. 1, No. 2 and No. 3.