The concept of scale v. gauge can sometimes prove hard to grasp, even for some experienced members of the G Scale community, never mind beginners. Many people manage to get huge enjoyment out of the hobby without having much regard for scale and gauge as long as they can run trains and this is no bad thing. It is not something you should develop a complex over but if you can come to terms with these key words it could help you avoid some costly mistakes.

As we have already mentioned, unlike our fellow modellers in the smaller scales such as OO, HO and N, where each scale is has individual and clearly delineated standards, the world of G Scale is a far more complex affair with a plethora of different scales all running on the same 45mm gauge track. As a result all trains made for large scale tend to get grouped under the same generic title and the indiscriminate use of the term "G Scale", often wrongly as an interchangeable synonym for "G Gauge" - only serves to complicate matters further. I am often guilty of this offence myself and will probably continue to do so in this series of articles!

In many hobby outlets, especially those which only carry a limited range of large-scale models, everything in this category can be lumped together creating a potential trap for the unwary. You really do need to do your research beforehand and keep your wits about you if you are striving for prototypical perfection.

However, provided one is not a stickler for absolute accuracy (and possibly compromising the integrity of your railroad layout) it is sometimes better to go with the flow on the age old premise that "if it looks right it is right".

Indeed many manufacturers (even including LGB who have never adhered rigidly to its stated scale ratio of 1:22.5 ever since Lehmann Brothers introduce G Scale Narrow Gauge as far back as 1967) appear to have taken considerable liberties with their published scales and adopted this rather more pragmatic approach  'selectively compressing' their models to fit an average size so that they will not look out-of-place when run together.

This 'laissez-faire' attitude is viewed as a compromise too far by some ardent rivet-counters (who would probably be happier constructing their own scratch-built models anyway - no offence intended) but for the majority of average modellers who are prepared to tolerate such practices, their enjoyment of the hobby is largely unaffected by such considerations.

So let us return to the vexed question of scale versus gauge. As someone once said two deceptively simple terms  but extremely important in the world of model trains. Knowing the difference and what to look for when selecting your very own train could be the difference in making a costly, time-consuming mistake or getting on the fast track to countless hours of enjoyment!

To put it simply "scale" is the proportion of the model relative to the actual prototype it represents in real life. Thus if a model is built to  1:24 scale every 1" of the model will be equivalent to 24" on the real thing. It is the same ratio in metric measurement where each 1mm of the model will represent 24mm of the prototype on which it was based. Scale can also be expressed as a fraction e.g. 1/24th as well as a ratio.

The term "gauge" is the distance between the inside head of the two rails which form the track which in G Gauge, or more accurately Gauge #1, is 45mm. You can learn more about rail sizes (codes) in a later Chapter devoted to track systems.

There you have it! Hopefully the foregoing explanation has not served to confuse you even more but it is essential to have a proper understanding of the meaning of these basic terms to get the best out your hobby.

The multiplicity of scales and gauges in popular use around the world for model and miniature railways is quite mind-boggling but some further information may help you  in choosing the right mix for your own large-scale layout - whether located indoors or more likely in the garden.

Below is a summary of some of the most common scale / gauge combinations but there is always someone, or even a group of like-minded enthusiasts, out there who has chosen to model in a unique format which may have escaped consideration. The smallest scale considered suitable for outdoor use is G Gauge but some intrepid modellers have successfully created al fresco layouts in O Gauge and even OO so if you fancy a challenge don't be put off.







Grand Scale

1:4 and over

3" / ft

3.5" - 32" (UK)

254 mm - 457 mm (Rest of World)


A ridable miniature railway (USA: 'riding railroad' or 'grand scale railroad') is a ground-level, large scale model railway that hauls passengers using locomotives that are models of full-sized railway locomotives (powered by diesel or petrol engines, live steam engines or electric motors). Usually found in amusement parks.  Link to Wikipedia

Ride-On or Live Steam


1½" / ft

184 mm or 190 mm or 45mm


Commonly used for ride-on trains such as 7¼" (184 mm) gauge, 1½" scale but also to model  15" trains on Gauge 1 track. Often Live Steam on 7.25" - 7.5" gauge track.

Live Steam


1" / ft

127 mm or 121 mm


Another ride-on gauge of either 5" (127 mm) in Europe but  4¾" in USA & Canada.

7/8 N2


7/8" / 1 ft (USA)


Narrow Gauge 2'

SE scale for modelling  2' (610 mm) gauge prototypes e.g. Maine 2- footers,  using 45mm track.

Live Steam


1⅓" / ft

3½" (89 mm)


Ride-able outdoor gauge used throughout the world.



16 mm / ft

32 mm

Narrow Gauge 2'

This scale was developed in the UK in the 1950s to represent  2-foot (610 mm) narrow gauge prototypes utilising 32 mm or "O gauge" track and wheels, but really took off in popularity during the 1960s and 70s. Originally, mostly used indoors but has now become a popular scale for garden railways depicting narrow gauge prototypes. 



5/8" / ft


Narrow Gauge

16 mm = 1 foot   But running on 45mm track!

F/Fn3 Scale


15 mm / ft


Narrow Gauge 3'

Scale introduced to depict North American 3-foot (914 mm) gauge trains in exact proportion to their correct track gauge whilst using 45 mm gauge model track. It equates to 15 mm = 1 foot (1 : 20.32) scale.  Fn3 scale, together with G scale, 1:29, 1:32 and ½ inch (1:24) scale, are commonly and collectively referred to as "Large Scale" by many modellers and this nomenclature has been endorsed by the National Model Railroad Association (NMRA) of America.

G Scale or G3  (Narrow Gauge)


13.5 mm / ft


Narrow Gauge 3' or 1 Metre

Equates to 0.533 inches = 1 foot !  Originally popularised by LGB from the German groß (meaning "big"), now also G as in Garden, G is widely used for garden railways of narrow gauge prototypes and uses the same track gauge as  Gauge 1.  Also called II m or 2 m in Europe.

H Scale


1/2" / ft (USA)


Narrow Gauge

Also a commonly available doll house scale.  An attempt to model North American and UK 3-foot (914 mm) narrow gauge or 3-foot-6-inch (1,067 mm) narrow gauge trains in better proportion to the rails they run on. Some Live Steam examples.

G Scale Gauge 2 (Standard Gauge)


Gauge 2 (USA)


Standard Gauge 4'8½"

Where 0 .414 in.= 1 foot - sometimes referred to as G64 in UK. The dominant scale used in the USA  for models of "standard gauge" trains running on 45 mm track, even though 1:32 is more prototypically correct.  1:29 represents standard gauge originally using 2" (50.8 mm) gauge track, hence the original name Gauge 2.  Some manufacturers kept the scale for the models but running them on slightly narrow gauge track.

Gauge 1 (Variant)


3/8"/ ft


Standard Gauge 4'8½"

Some manufacturers offer Gauge 1 items in 1:30.48 scale ( 10 mm to 1' scale).

Gauge 1


3/8"/ ft


Standard Gauge 4'8½"

Where inch (USA) or 10 mm (UK) = 1 foot.  Now increasingly used for modelling standard gauge trains as garden railways (especially in the USA).

L Gauge

1:38 nominal




Unofficial designation of toy trains built from LEGO. Can be custom built to differing widths according to the track gauge.

Gauge 0 or O Scale


Gauge ‘0 (UK & France)

32 mm

Standard Gauge 4'8½"

7 mm: 1 foot scale - Sometimes called 7 mm Scale or Scale 7 (33 mm Gauge). Originally called '0' (zero) as numbers 1 - 6 were already taken for larger scales. Often used for toy trains where scale accuracy is less important.

Gauge 0 or O Scale


Gauge ‘0 (Germany)

32 mm

Standard Gauge 4'8½"

O Gauge was originally introduced by German toy manufacturer Märklin around 1900 which became popular throughout Europe and ultimately worldwide. Lionel, LLC, MTH and Atlas are major manufacturers in this scale.

Gauge '0' or O Scale or ¼" scale (USA)


¼" / ft

32 mm

Standard Gauge 4'8½"

 North American version of O gauge popularised by Lionel Trains. This is also a common doll house scale affording  more options for figures, buildings, and accessories.  1:43 scale model cars can also be used for scenic effect.

Proto 48



29.90 mm


Same scale as US 0 Gauge above but built to more accurate dimensions.


Note:  Some of these scales are recognised around the world whilst others are little known outside the country of origin. The National Model Railroad Association (NMRA) in the USA and MOROP (NEM -  Normen Europäischer Modellbahnen (NEM) in Europe are the custodians of rail transport modelling standards  in an attempt to bring some standardisation across the globe.


REMINDER:  If you are modelling in G or "Large Scale" the important thing to remember is that the track is always 45mm wide and the scales change in accordance with the prototype gauge you want to reproduce on your layout.

© Copyright : John Prescott - 2009

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