2mm scale, often 2mm finescale is a specification used for railway modelling, largely for modelling British railway prototypes. It uses a scale of 2 mm on the model to 1-foot on the prototype, which scales out to 1:152. It is, therefore, similar in size to the slightly larger British N scale at 1:148 and the slightly smaller European/American N scale at 1:160; it predates both versions of N scale. The track gauge used to represent prototype standard gauge (4'8½") is 9.42 mm (0.371 in), 0.41 mm wider than commercial 9mm N gauge. Track and wheels are closer to scale replicas than commercial N; the track is only 1 mm high. No ready-to-run models are available in 2mm scale, and although there is some availability of kits and components, some model-making skill is normally required.
Since 2mm scale is very close to the 1:148 British N scale, a hybrid specification can be modelled by rewheeling proprietary British N scale models to the 9.42 mm track gauge. This hybrid specification results in a track gauge equivalent to 4 feet 6⅞ inches (1394mm), slightly narrower than the prototype 4 feet 8½ inches. There is an advantage however in the narrower gauge as this allows more room for the outside motion of outside cylindered steam locomotives which must be overscale in order to function correctly. This approach is often recommended for beginners. However, 2mm-scale and hybrid-scale models do not usually sit well together due to the larger size of the latter.
Modelling the Irish broad gauge (5'3") and Great Western broad gauge (7') is also possible to 2mm standards.
There is an active association, The 2mm Scale Association, for modellers in this scale, who supply components, tools and jigs, publish a bi-monthly magazine, organise local chapters, and promote modelling in the scale.