In the world of railway modelling and model trains, there are a vast range of scales/gauges available; Many of the scales have been developed by purists in a drive to improve accuracy and realism of previous scales/gauges. But by far the most common scales and most widely available worldwide are 00, HO and N. Many others require specialist support and lie firmly in the realm of scratch builders and specialist modellers.
Historically there are broadly two main groups:
- “Standard gauge”, based on a 4ft 8½in prototype.
- “Narrow gauge”, which refers to any railway with a track gauge that is less than “standard gauge”.
Standard Model Railway Gauges
- 00 Gauge: 4mm to 1ft, 1:76 scale
16.5mm gauge (inside track width)OO gauge is a British modelling standard, which is extremely popular, with a diverse and indeed abundant range of ready-to-run models, kits and accessories. Whilst it’s the most popular gauge, technically the track gauge is around 15% under scale (18.83mm would be correct)
- 1 Gauge: 10mm to 1ft, 1:30.5 scale
44.45 gauge (track width)Pretty much the largest scale used for standard (and narrow) gauge models. Many models and locomotives are scratch built in this gauge but some very expensive, ready-to-run models are available in Continental Europe.
- 0 Gauge: 7mm to 1ft, 1:43.5 scale
32mm gauge (inside track width)Becoming more and more popular due to the availability of a large range of quality locomotive and rolling stock kits in this scale.
- S Gauge: 4.76mm to 1ft, 1:64 scale
22.2mm gauge (track width)One of the most accurate available with an almost perfect scale/gauge ratio, it lies between 0 and 00. Very little commercial support from the manufacturers except in the USA.
- EM Gauge: 4mm to 1ft, 1:76 scale
18.2mm gauge (inside track width)Em makes a bid to make the OO layout track gauge more realistic. At 18.2mm it’s still not a scale perfect 18.83mm, but it’s pretty close.
- P4 Gauge: 4mm to 1ft, 1:76 scale
18.83mm gauge (inside track width)Created to supersede Em and remove the scale inaccuracies. Locomotive and rolling stock kits are available P4 making it slightly more popular than Em.
- HO Gauge
3.5mm to 1ft, 1:87 scale
16.5mm gauge (inside track width)By far the most popular gauge outside the UK. At 3.5mm to 1ft, the track gauge of 16.5mm is near enough exact to scale for the standard gauge railways. Although it uses the same track gauge as OO, HO gauge is around 15% smaller than its 1:76 OO cousin. Running HO gauge rolling stock on 00 gauge layouts is perfectly feasible, but there may be some visible differences in the scales.
- TT Gauge: 3mm to 1ft, 1:101.6 scale
12mm gauge (inside track width)Originating from the USA, TT Gauge was also produced at 2.5mm to 1ft, 1:120 scale. Specialist support for this scale can be found through the Three Millimetre Society.
- N Gauge: 2mm to 1ft, 1:148 scale in UK
9mm gauge (inside track width)British N gauge is half the size of 00 and in theory you should be able to lay around 4 times the amount of track in any given space compared to OO. Becomming very popular due to the huge range of locomotives, rolling stock and accessories. In Europe and North America the scale of 1:160 is used for N gauge models, running on 9mm gauge track.
- 2mm Scale: 2mm to 1ft, 1:152.3 scale
9.42mm gauge (inside track width)Developed by N gauge purists. More accurate than the mainstream scale of 1:148.
- Z Gauge: 1.5mm to 1ft, 1:200 scale
6.5mm gauge (inside track width)This is a commercial gauge manufactured primarily by Marklin. Relatively expensive and specialist, but more support, internationally at least is developing.