There is some confusion and continued misinterpretation about the terms ‘scale’ and ‘gauge’ as they relate to model trains.
To add to the confusion, model train enthusiasts, and indeed some model train manufacturers, sometimes use the terms ‘gauge’ and ‘scale’ interchangeably and model trains of the same scale can run on different gauges.
Scale is referring to the ratio of the size of a model train compared to the full size train on which it is modeled. For example, Ho scale model trains are 1/48th the size of the actual railway locomotives and rolling stock they are copying.
Gauge however is the measurement between the inside edge of the rails on which the trains run. As with the scale ratios which determine the size of model trains, so gauge is a ratio of the distances ‘real’ train lines are set apart.
The ‘standard gauge’ used on most railways throughout the world is 4 feet 8½ inches, so most model train gauges are based on a proportion of that. However, there is considerable variation, with ‘broad’ and ‘narrow’ gauge versions widely used.
In addition, some model trains are designed to run on gauges which are ratios of the 5 foot gauge railways found in some parts of the world.
Because which train scale you want to use is the first and most important decision you will need to make when setting up your first model train layout it is essential to have a clear understanding of what the terms ‘scale’ and ‘gauge’ actually mean.