What is the difference between gauge and scale in model railways?

Gauge refers to the distance between the two rails on the track. It represents the real-world measurement of the spacing between rails on a full-size railway. In the UK, the most common model railway gauges are:

• OO gauge (4mm to the foot or 1:76.2 scale)
• OO9 gauge (9mm or 1:76.2 scale narrow gauge)
• O gauge (7mm to the foot or 1:48 scale)
• N gauge (2mm to the foot or 1:148 scale)

Scale refers to the ratio of the model size compared to the real prototype. It dictates how large or small the models (locomotives, rolling stock, scenery, etc.) are in proportion to their full-size counterparts. Common scales include:

• 4mm scale (1:76.2) matching OO gauge
• 7mm scale (1:48) matching O gauge
• 2mm scale (1:148) for N gauge

So in summary, the gauge determines the track width, while the scale sets the overall size of the models relative to reality. Models of the same scale can run on different gauge tracks for variety.