Gauge & Scale

model trains for beginners

Gauge & Scale

Probably one of the first decisions you will make with respect to your model railroad is the question of scale.  What scale would you want?  HO or N or O or S, or would you want a garden scale?  What is scale and gauge?  Let’s demystify this a bit for you.  In short, scale is the ratio of the model to the real item, and gauge is the distance between the rails.

Scale Explained

The term scale implies the scaled down version of the actual object. O scale formally known as ¼ inch scale, has a ratio to the actual object as 1:48. HO is 1/8 inch scale and 1:86 or 1:87. There have been some minor changes in HO and it is now 3.5 mm and 1:87.1.  N scale is 1:160. Let’s look at sizes.  Of the traditional scales, O is the larger. Lionel O27 as an example is not truly O scale. S scale is smaller than O and was derived from American Flyer. The next size is HO and can be referred to as Half O, N scale being about half of that.  Z scale is the smallest scale, and is at 1:220.

There are a large selection of quality products which are available in both HO and N scales. S scale is however growing rapidly.  As a modeler, the selection is your choice. N scale allows you to have really long trains.  HO appears to be the better scale, the reason being that HO allows trouble free switching for yard switching, way-freights and local switching operations. Always remember, the larger the scale, the more room is required for an extensive layout. Your choice of scale will be dependent on what you wish your railroad to do. What should be mentioned is that you can’t have twice the N scale railroad on a 4×8 as an HO scale.  The reason for this is that they do not scale out exactly and they have requirements that will need you to design the railroad in order to fit the space, rather than using the other scale’s track plan.  We have omitted to mention OO and TT, but they are in the minority, but have their own proponents.

Gauge Explained.

Let us get into the definition of gauge.  What is gauge?  Gauge is the distance between the tracks. 4’8 ½” is the normal track gauge.  If we take HO as an example, HOn3 can be defined as HO scale, narrow gauge, and three feet between the rails.  HOn2 can be defined as HO Scale, narrow gauge and two feet between the rails. This notation can be a little different, for example HOn30 is HO scale, narrow gauge and 30 inches between the rails.

S scale narrow gauge is becoming very popular and growing quite fast, the reason being you can fit a nice size narrow gauge layout into an area that is not much bigger than an average HO layout.  A number of modelers have adopted S scale since the release of Bachmann’s On30 train set, as they can have O scale buildings and people with a smaller train that can run on track about the size of HO.  Always think ahead, as you may appreciate larger objects as you get older.

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S scale narrow gauge is growing because you can put a nice size narrow gauge layout into a space not much bigger than a modest HO layout. With the release of Bachmann’s On30 train set, a number of modelers have jumped on it as they can have O scale people and buildings with smaller trains that run on track about the size of HO. As you get older, you sometimes appreciate larger buildings and cars etc.

A table is provided below as a quick reference.




O(17) .266″(6.75mm) 1:45.2
O,On3,On2 .250″(6.35mm) 1:48
S,Sn3 .188″(4.76mm) 1:64
OO 4.0mm(.1575″) 1:76.2
HO,HOn3,HOn2 3.5mm(.1378″) 1:87.1
TT, TTn3 .100″(2.54mm) 1:120
N, Nn3 .075″(1.90mm) 1:160
Z .055″(1.39mm) 1:220

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