Beginner's Guide to Model Railroading

What Does Scale Mean?

Definition of Scale
The size of the model train as compared to the size of its actual prototype and expressed as a ratio.

The size of a model train is called its scale, which simply means how big it is compared to the size of its actual prototype (or the real train). Scale refers to locomotives, rolling stock (railroad cars), and even to buildings and other model railroading accessories.

Z-scale trains are scaled at 1/220 (the smallest scale) or only 1/220th the size of their prototypes (another way to express scale is in ratio form or 1:220 — 1/220 and 1:220 mean the same thing. N-scale is 1/160 (or 1:160), HO-scale is 1/87 (or 1:87), S-scale is 1/64 (or 1:64), and O-scale is 1/48 (or 1:48) and is the largest indoor model train).

There is also a G-scale (1/22 or 1:22) and this is called a garden scale, because these trains are used mostly for outdoor railroading. G-scale model trains are very large. Some people refer to model trains as HO-gauge or S-gauge or O-gauge. This is incorrect. Model trains are always referred to by their scale.

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What Is Gauge?

More On Scale

Think of scale as a ratio; that is, how much smaller or larger something is to a similar object. The object may be a bronze statue in a park. If you are five feet tall and the statue is ten feet tall, you are half as tall as the statue. If we compare your height to the height of the statue in terms of ratio, you would be 1/2 the height of the statue (a 1:2 ratio). Of course, scale is a bit more complicated than simple ratio. Although you would be 1/2 as tall as the statue, we would not know how wide you were to the statue. Scale defines height, width, and depth (volume). An HO locomotive with a scale of 1:87 would be just as high, and wide, and deep as its prototype if it were enlarged by 87 times. To state it another way, the enlarged HO-scale model locomotive would possess the same shape and volume as the prototype.