List of rail transport modelling scale standards

While the most significant standardised dimension of a model railway scale is the gauge, a typical scale standard covers many more aspects of model railways and defines scale-specific dimensions for items like catenary, rolling stock wheels, loading gauge, curve radii and grades for slopes, for instance.

Narrow gauges are indicated by an additional letter added after the base scale as follows: For instance, a metre-gauge model railway in H0-scale is designated H0m.

NMRA standards are used widely in North America and by certain special interest groups all over the world.

This is one of the main reasons why the country has traditionally used its own distinctive model railway scales which can rarely be found outside the British Isles.

The globally more-widespread international NEM and NMRA scale standards are relatively rare in Great Britain and used almost exclusively by those modelling foreign prototypes.

While there are Japanese model railway manufacturers that export their products to other parts of the world and follow the scale standards of the export destinations, in Japan there are several domestic scales that are popular in the country but virtually unknown elsewhere.

One example is the "IBLS" (International Brotherhood of Live Steamers), an informal organization which has published standards for some of the gauges.

Locomotives in this scale are generally large and "chunky", and can range from the tiny 0-4-0 seen on Welsh slate quarry lines all the way up to the very largest found in the UK, such as the ex-ACR NG/G16 Beyer-Garratt locomotives, seen running on the Welsh Highland Railway in North Wales.

The hobby is supported by a number of 16 mm live steam and electric traction builders, dominated by the likes of Roundhouse Engineering and Accucraft UK.

They use a "scale" appropriate to the original prototype modelling both standard and narrow gauge locomotives to run on 2.5-inch track.