Which scale is "Best"

This article first appeared in the September/October 1990 issue of AMRA's 'Journal'.
By Steve J Chapman.

One of the earliest decisions that needs to be made when building a model railway is the scale to which the model is to be built and the track gauge. Most people involved in building model railways are heavily committed to one scale or another and rarely stop to consider whether or not the scale to which they are working is the best one. Scale can sometimes make all the difference as to whether or not you have sufficient space to build the desired layout. The appearance of the finished layout will also be affected by the parts of the model being squashed together to squeeze them in or by the larger open spaces where you have plenty of room.

The space that a given model takes up is obviously not the only consideration or everyone would be working in Z gauge. Also of concern is how much that you want to fit in, the aspects of Railway Modelling in which you are interested, the type of operation that you require, availability of suitable models, and personal comfort.

Let us stop now and consider some of the different scales and what the advantages and disadvantages of these scale are. This will be of particular interest to beginners who are not yet committed to one scale. It will also enable those who have chosen a scale to see whether the scale that they have chosen is suitable or if there is a "better" scale that they could have chosen. Perhaps the benefits to be achieved may make a change of scale worthwhile.


In the beginning there were four scales that were used to build model railways. These were called one gauge, two gauge, three gauge, and four gauge. Each of these scales was fairly large and therefore required a lot of room for even the simplest of layouts. These scales were therefore mostly used in the garden by model railway and live steam enthusiasts alike. These scales (in particular one gauge) are still used by the live steam enthusiasts but most railway modellers now work in the smaller scales.


The next scale to be developed was smaller than one gauge and hence received the next number smaller than one which is zero. Of course a zero and an "Oh" look very much alike and the scale soon became known as O gauge. This scale has become very popular again over the last few years as people have rediscovered its benefits.

O gauge is ideal for garden layouts as its size enables very robust models to be built. It is also a large enough scale to enable scratchbuilding of models with a much greater level of detail than in the smaller scales. For those short on space a small shunting layout and a small number of super-detailed models in O gauge is one alternative that should be considered.

O gauge does not permit long trains unless an enormous amount of space is available but it does permit highly detailed short trains. As has been shown in some of the modelling magazines recently O gauge layouts can be built in a relatively small space (5' by 1' being quite possible). A small layout perhaps needs the larger scale so that the small details can be included which you would not have time to include if your layout was larger. At least in O gauge it is possible to see the smaller detail so that other people will know that its there without you having to tell them.

The amount of ready to run stock in O gauge is relatively small but this is fairly unimportant because the large size of O gauge makes kit and scratch building easier than in the smaller scales (at least you can see the pieces).


The most popular scale today is HO (or OO in Britain). The name HO came about because the scale is Half that of O gauge. OO was developed in England on the same gauge track but using a slightly larger scale because the smaller loading gauge in England made it difficult to get even the smallest motors of the day into HO models of British locomotives. These scales being relatively close in size have basically the same advantages and disadvantages and so I shall discuss them together.

HO being only half the size of O gauge enables four times as much railway to be built in the same space (or three times as much for OO). Trains can have twice as many wagons or coaches as would be practical on an O gauge layout in the same space or if train lengths are left the same then more complex track work and a larger number of trains can be fitted in. HO is still a large enough scale for a reasonable amount of detail to be included although not quite as much and not quite as easily as could be done on an O gauge layout.

Being an intermediate size (between O and N) HO scale shares some of the advantages and disadvantages of both. It is a compromise scale that enables the person who wants to include both detail and long trains to be able to get at least a little of each.

There is an enormous amount of ready to run stock available in HO/OO, more so than in any other scale. This makes the construction of a proprietary layout where all of the rolling stock is off the shelf a relatively easy matter. The similarly wide range of kits and scratch building components also makes it suitable for the beginners layout where it is intended to move on to kit building and scratchbuilding as soon as the owner feels that he is ready.


The other popular scale today is N gauge. It is called N gauge because the track gauge is nine millimetres and N is the first letter of the word "nine" in most countries where N gauge is used.

The advantage of N gauge is that because it is so small there is room to run long trains. A four coach passenger train in N gauge may be only slightly longer than an O gauge locomotive. Also with N gauge it is possible to fit in a reasonable amount of the surrounding countryside and still have enough space for the trains. With N gauge you can achieve the effect of full length trains running through open countryside without needing an aircraft hanger to house the layout.

The disadvantage of N gauge is that it is so small. Because N gauge is so small it is very difficult to include many of the small details that it is possible to include in the larger scales. Even when you find a way to include the small detail you are very likely wasting effort because it will be so small that many people will not be aware that its there (except for you of course). Therefore the aim with N gauge should be the broad picture rather than the smaller details. N gauge can be used for small shunting layouts but does not appear as realistic as can be achieved with a larger scale. N gauge works best with long trains and plenty of open countryside. Thus it (paradoxically) really needs more room than layouts built in the larger scales.

There is a reasonable amount of ready to run stock available in N gauge, especially for those who model American. Kits and scratch building components also exist although constructing models is made more difficult by the smaller size of the models.


There are other scales that some people work in which have advantages and disadvantages all of their own but these scales are not commonly available to the beginner and hence have been specifically chosen to satisfy the particular requirements of the people using them in order to satisfy some particular requirement that the particular modeller has.

Most of these "specialist" scales have little, if any, ready to run stock available. Some of these scales are more popular with people Modelling particular prototypes and have a large range of ready to run stock for their given prototype and nothing else. Some are designed so as to be able to make use of many of the kits and scratch building components that are primarily intended for one of the other scales. In any case choosing one of these scales also limits some of your other choices (which doesn't matter if the limitations are what you would have chosen anyway).


All of the scales mentioned so far are intended to be used to model standard gauge lines. Not all lines modelled are standard gauge. Some people model broad gauge or narrow gauge. These scales have similar advantages and disadvantages to the standard gauge scales of similar size. Track gauge does however have an effect on what can be done particularly with regard to space requirements.

Narrow gauge seems much more popular than broad gauge. Perhaps this is because it allows the same amount of detail as a standard gauge layout in the same scale but can be squeezed into a smaller space because of shorter trains and tighter curves.

HOn3 (OO9) allows the detail of an HO layout in a fraction of the space. This scale/gauge combination also has the advantage that N gauge track and mechanisms may be used together with HO scale scenic features (in addition to those items supplied by the trade specifically for this gauge).

G gauge requires a similar space to O gauge but permits much more detail.

Both of these scales have a reasonable amount of ready to run stock available for them although the range is not quite as wide as with some of the standard gauge scales that I have mentioned. Many of the kits etc intended for use with standard gauge may also be used or adapted for use with narrow or broad gauge.


Actually there is no scale that is better overall than any other scale. The scale to which various model railways should be built depends entirely on the purpose that the model railway has, the amount of space that the builder has in which to build the layout, and the physical capabilities of the builder. For most modellers the best scale for them to work in is the scale that they are working in now.

There is nothing says that you can't build a shunting layout in a space of 5' by 1' in N gauge, its just that you can include a lot more of the small detail if you use O gauge (and be able to see that its there). A 20' by 10' O gauge layout can be built but will you have the time to properly detail it, a similarly sized N gauge layout doesn't need as much detail to look good.

If you are happy with the scale that you are working with now, especially if you have a layout under construction (or perhaps already built) then you have no reason to change.

If you are not yet committed or want to change scales then stop to consider the advantages and disadvantages of the various scales. What is it that you want to achieve and which scale is the most suitable with which to achieve your objectives. You don't even need to agree with me as to what the advantages and disadvantages are. A little thought in choosing the right scale before you start can sometimes make all the difference.


Scale Chart

 Scale        Ratio       mm/ft        gauge
   4          1:15         20
   3          1:18         17
   2          1:23         13
   1          1:30.5       10           45      British
   1          1:32          9.5         45      Continental
   1          1:32         3/8in       1-3/4in  American
** O          1:43.5        7           32
   O          1:45          6.8         32      Continental
   O          1:48         1/4in       1-1/4in  American
   Q          1:48         1/4in      1-3/16in
   S          1:64        3/16in         7/8in
   OO         1:76.2        4           19      American
   P4/S4      1:76.2        4           18.83
   EM         1:76.2        4           18
** OO         1:76.2        4           16.5    British
** HO         1:87.1        3.5         16.5
   TT         1:100         3           13      Continental
   TT3        1:101.6       3           12      British
   TT         1:120         2.54        12
   N          1:148         2-1/16       9      British
   OOO        1:152         2            9.5
** N          1:160         1.9          9
   Z          1:220         1.4          6
   SM45       1:19         16           45
   SM32       1:19         16           32
** G          1:22         14           45      LGB
   OM         1:48          7           22.5
   On3        1:48         1/4in        19      O on OO American
   On2        1:48          7           16.5
   Sn3-1/2    1:64         3/16in       16.5
   OOn3       1:76.2         4          12      OO on TT (British)
** OO9        1:76.2         4           9      OO British on N
   OO6        1:76.2         4           6      OO British on Z
   HOm        1:87.1         3.5        12      HO on TT
** HOn3       1:87.1         3.5        10.5
   HOn2-1/2   1:87.1         3.5         9      HO on N
   HOn2       1:87.1         3.5         6      HO on Z
   TTn3       1:101.6        3           9      TT3 on N
   Nm         1:160          1.9         6      N on Z

Note: scales marked ** are discussed in the above article and are the more common scales in use today.

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Copyright Stephen Chapman