Model Train Gauge vs. Model Train Scale

[John G Spencer]

For many people new to model railroading, the question of model train gauge versus model train scale can be quite confusing. Here’s a simple explanation. Gauge is the measurement of distance between the two outside rails of the track. Model train gauges have been standardized to assist in easy identification of these specific dimensions.

Model train scale is simply the fractional equivalent for the gauge, and inches are used as the units of measurement. For example, a model train designated as 1:48 scale dictates that 1″ of the model train equates to 48″ of the train it was modeled after.

Here’s a helpful chart:

Gauge Designation --- Distance Between Rails --- Scale

Standard --- 2.125″ (54mm) --- 1:24

G --- 1.75″ (45mm) --- 1:22.5 or 1:20.3

No. 1 --- 1.75″ (45mm) --- 1:29 or 1:32

O* --- 1.25″ (32mm)* --- 1:48

Proto-48 --- 1.169″ (43mm) --- 1:48

S --- .875″ (22.5mm) --- 1:64

OO --- .75″ (19mm) --- 1:76

HO --- .650″ (16.5mm) --- 1:87.1

TT --- .471″ (12mm) --- 1:120

N --- .354″ (9mm) --- 1:160

Z --- .256″ (6mm) --- 1:220


* O gauge measures the distance from the center of each of the two outside rails.


Hopefully, this will help clear up some of the confusion regarding train gauge and train scale for all you model railroading enthusiasts. For more great information on model railroading, rolling stock, scenery, and railroading history, please visit this great model railroading resource -- The Model Train Hobbyist

Happy Railroading!!

John G. Spencer
The Model Train Hobbyist