| 7 mm scale | |
| Image Filename: | Locomotor model.jpg |
| Image Caption: | O gauge layout at the Trains and Boats exhibition |
| Widthpx: | 270 px |
| Scale: | 7 mm to 1 ft |
| Ratio: | 1:43.5 |
| Gauge: | multiple |
7 mm scale, also known as British O scale is a model railway scale of 1:43.5 (or 7 mm to 1 ft; hence its name). The scale is thus different from American O scale (1:48) and European O scale (1:45). For standard gauge railways, 32mm gauge, or 0 gauge is most commonly used. ScaleSeven (S7) standard however specifies 33 mm gauge, which is closer to scale.[1] For narrow gauge modelling, 16.5 mm gauge
| Name | Model gauge | Scaled gauge | Prototype gauge | |
|---|---|---|---|---|
| Prototype standard gauges | ||||
| 32 mm (0 gauge) | 4' 6¾" | Standard gauge | ||
| ScaleSeven (standard) | 33 mm | 4' 8½" | ||
| Prototype broad gauges | ||||
| ScaleSeven (Irish) | 36.75 mm | 5' 3" | ||
| ScaleSeven (Great Western) | 49.2 mm | 7' 0¼" | Great Western broad gauge | |
| Prototype narrow gauges | ||||
| 21 mm | 3' | |||
| 16.5 mm (H0 gauge) | 2' 4¼" | 2' - 2'6" | ||
| 14 mm | 2' | |||
| O9 | 9 mm (N gauge) | 15½" |