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Primo Models Blog

Popular Model Railway Gauges and Scales

Post by: Michal Kmiec #Primo Models

With such a wide variety of scales and gauges available to railway modellers it can become challenging to decide which product is right for you. This guide explains the differences between some of the most commonly used model rail scales and gauges. 

What Is the difference between scale and gauge?

It is essential to understand the difference between scale and gauge. Scale refers to the physical size of the model in relation to the original object, for example, a 1:76 scale model is 1/76th the size of its real-world counterpart. As a rough guide, the larger the scale number, the smaller the model.
Gauge refers to the distance between the rails – different gauge models and track have a standard measurement for that gauge between the wheels and rails. However, this is where the difference between scale and gauge becomes important – different scale models can run on the same track if the gauge is the same.

List of Main Model Railway Gauges.

GAUGE DESCRIPTION (Gauge=inside track width)
Z 1.5mm to 1ft, 1:200 scale – 6.5mm gauge
N 2mm to 1ft, 1:148 scale in the UK (1:160 some countries): - 9mm gauge
H0 3.5mm to 1ft, 1:87 scale - 16.5mm gauge ACCURATE SCALE TO GAUGE
OO 4mm to 1ft, 1:76 scale - 16.5mm gauge NOT ACCURATE SCALE TO GAUGE
S 1.435 mm to 4ft 8 ½ in, scale 1:64 – 22.43 mm gauge
O 7mm to 1ft, 1:43.5 scale – 32mm gauge
1 10mm to 1ft 1:32 scale – 45mm gauge
G 1:22.5 – 45mm (1.75 in) gauge

Z SCALE / GAUGE 1:200 

At a ratio of just 1:220, Z Gauge is the smallest model railway scale in everyday use, and yet achieves stunning levels of detail and accuracy. German Maerklin is the leading player on the market for this gauge. It is relatively expensive and specialist.

N SCALE / GAUGE 1:148 (1:160) 

This gauge is half the size of 00, and therefore you should, in theory, be able to lay four times as much track. It is becoming a very popular gauge with a full range of locomotives, rolling stock and accessories available from many companies. N Gauge differs slightly depending on the region of manufacture from 1:148 up to 1:160 (UK brands are generally 1:148). However, as with H0 and 00, both have the same gauge.

H0 SCALE / GAUGE 1:87 

HO is the primary gauge used outside the UK. At 3.5mm to 1ft, the track gauge at 16.5mm is virtually exact to scale for the standard gauge. When using this gauge, it must not be confused with the 00 gauge. Ho gauge is almost 15% smaller. One can run HO gauge rolling stock on 00 gauge layouts and vice versa, the track gauges both being 16.5mm, but the difference in scale will immediately become apparent.

OO SCALE / GAUGE 1:76 

HO is the primary gauge used outside the UK. At 3.5mm to 1ft, the track gauge at 16.5mm is virtually exact to scale for the standard gauge. When using this gauge, it must not be confused with the 00 gauge. Ho gauge is almost 15% smaller. One can run HO gauge rolling stock on 00 gauge layouts and vice versa, the track gauges both being 16.5mm, but the difference in scale will immediately become apparent.

S SCALE / GAUGE 1:64

This size originated with the American Flyer brand of model trains in 1946, and it’s the oldest known railroad modelling scale. It is about halfway between the O and HO size and was very popular in the 1950s (it’s recently started to gain more popularity). Models are 1:64 scale and run on a 22.43mm gauge track. This gauge is extremely popular around American railroad enthusiasts.

O SCALE / GAUGE 1:43.5

Popular scale during the period, when model railways were considered toys during the ’60s & ’70s. Detail and realism were a secondary concern for those. It is still popular among collectors, and recently it started gaining popularity in modellers environments.

1 SCALE / GAUGE 1:32

This scale is mainly used outside for electric and live steam operation. Interestingly this scale was used for the model locomotives and rolling stock in seasons 1 to 12 of THOMAS & Friends before switching to CGI animation.

G SCALE / GAUGE 1:22.5


This gauge is used mainly for outdoor models (garden railways), because of its size and durability. Modellers use the outdoor landscape like hills, lakes, ponds, etc. as elements of layout for the train operation. Unfortunately, due to its size, G sale is the most expensive scale and requires a lot of space to run.

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