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Sample list of British; model scale standards

An important factor to understand is the difference between gauge and scale. Like real-world railways, the gauge is the distance between the rails, with trains and rolling stock built for each particular gauge; scale is the proportion that the size of the model is compared to its real-world equivalent. The scale is normally expressed as a ratio (1:16 or 1/16) or a size (1 inch :1 foot). Sounds simple enough? Not quite! When a model train is scaled down, the gauge is not necessarily to scale, but to the nearest standard gauge. This means that you could have two different trains, both with the same gauge, but a slightly different scale. In practice, this will be hardly noticeable, but it is worth bearing mind.


The main railways in Great Britain use the international standard gauge of 1,435 mm (4 ft 8 1⁄2 in) but the loading gauge is narrower and lower than in the rest of Europe with the same standard gauge. 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.

When H0 scale was being introduced, the motors available were too large[ to fit in scale-sized bodies and so as a compromise the scale was increased from 3.5mm to 4 mm to the foot, but the gauge was not changed so other elements could be shared. For 00 therefore the track is narrower than it should be for the scale used. In more recent times, small motors have become available and so the advent of EM and ProtoFour scales correct this anomaly by adopting a wider track gauge.

Scale Ratio Gauge Notes

000 scale or 2 mm 1:152 9.42 mm (0.371 in) An early predecessor of small scales like N. Developed before World War II and became somewhat popular in the 1950’s. No commercial products available. Today The 2 mm Scale Association is the force behind the scale and 2 mm scale has become a finescale alternative to the British N-scale.

N scale 1:148 9 mm (0.354 in) A British adaptation of N-scale for modelling British prototypes with a smaller loading gauge. Has a track gauge error of approximately 7%. Hobbyists who model European or American prototypes in Britain, use the standard N-scale with the scale ratio 1:160.

TT/TT3 scale or 3 mm 1:102 12 mm (0.472 in) Introduced by Triang in 1957 as a British adaptation of the American TT scale. Later Triang dropped this scale in favour of N scale and today there is no commercial following. Has a track gauge error of approximately 15%.

H0 scale or 3.5 mm 1:87 16.5 mm (0.650 in) H0 scale was introduced in Britain in the 1920’s. No commercial following? and used by only a small number of modellers to model the British prototype. There may be comments regarding this statement!


00 scale or 4 mm 1:76 16.5 mm (0.650 in) The most popular railway modelling scale in Britain. Has a track gauge error of approximately 12%.

EM scale or 4 mm 1:76 18.2 mm (0.717 in) This gauge is represented by the EM Society (in full, Eighteen Millimetre Society). 00 track (16.5 mm) is the wrong gauge for 1:76 scale, but use of an 18.2 mm (0.717 in) gauge track is accepted as the most popular compromise towards scale dimensions without having to make significant modifications to ready-to-run models. Has a track gauge error of approximately 3%.


P4 scale (Protofour)/S4 (Scalefour) or 4 mm 1:76.2 18.83 mm (0.741 in) Uses a track gauge of 18.83 mm which represents an exact scaling down of the prototype at 4 mm to 1 ft scale. As a scaling down of prototype dimensions with, in the case of P4 standards but not S4 standards, only slight modifications from true proportionality, the standards also specify wheel profile and other track dimensions as well as the track gauge. The standards set by the Scalefour Society are now applied to other prototypical track gauges.

‘S’ Gauge The proportion is 1:64 or 3/16" equals 1 foot.

(Standard "S" gauge is 7/8").

Three foot gauge in "S" Scale (Sn3 gauge) is 9/16".

O14 scale 1:43.5 14 mm (0.551 in) For accurately representing 2 ft narrow gauge in 7 mm scale.

‘O’ Gauge or 7 mm 1:43.5 32 mm (1.260 in) Three sub-standards: Coarse, Unified and Fine. Has a track gauge error of approximately 3%.

ScaleSeven (S7) 7 mm 1:43.533 mm (1.299 in) A finescale scale represented by The ScaleSeven group.

Wherever you are and which ever scale you decide to use The WWW; can offer you support, give model associations/club locations, give help and advice, find you many friends.


But above all else your models will help you realize your potential and give many hours of enjoyment with a little frustration thrown in.

Enjoy Modelling and building your very own railway, model, or engineering project of your choice..

Model Railway Scales and Standards 1.

This page contains a few notes regarding scales and ratios in the UK with links to the European and USA. Not all are shown but the important perspective for the Potential modeller/researcher or interested party is to decide what part the various organisation codes and standards will have an effect on their modelling and which direction to choose or maybe provide more help and support in their chosen scale.


We have included links to the following sites to help give an informative or better perspective on modelling standards for all our visitors.

Morop; (NEM Standards Web Site).                 



NMRA; (National Model Railroad Association).  ( Also: See article on the following page.)


Wikipedia organisation/Model railway scales.   


'G Scale' and 'G Gauge                                   

http://en.wikipedia.org/wiki/G_scale   ( Also: See article on the following page.)

MOROP is the European federation that groups and heads the different national federations for railroad modellers and railroad friends in Europe.

The NMRA is a non-profit corporation. It has a President and other officers and a Board of Directors. The Headquarters of the NMRA are in Chattanooga, Tennessee.

Wikipedia is an open source site that allows its users to add to its pages.

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