7 mm scale

7 mm scale, also known as British 0 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 0 scale (1:48) and European 0 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. For narrow gauge modelling, 16.5 mm gauge

Name	Model gauge	Scaled gauge	Prototype gauge
Prototype standard gauges
British 0 gauge	32 mm (0 gauge)	4' 6¾"[citation needed]	Standard gauge
ScaleSeven (standard)	33 mm	4' 8½"	4 ft 8+1⁄2 in (1,435 mm) standard gauge
Prototype broad gauges
ScaleSeven (Irish)	36.75 mm	5' 3"	5 ft 3 in (1,600 mm) Irish gauge
ScaleSeven (Great Western)	49.2 mm	7' 0¼"	7 ft (2,134 mm) Great Western broad gauge
Prototype narrow gauges
O21	21 mm	3'	3 ft (914 mm)
O16.5	16.5 mm (H0 gauge)	2' 4¼"	2' - 2'6"
O14	14 mm	2'	2 ft (610 mm)
O9	9 mm (N gauge)	15½"	15 in (381 mm)

7 mm scale
O gauge layout at the Trains and Boats exhibition
Scale	7 mm to 1 ft
Scale ratio	1:43.5
Model gauge	multiple

References