Scale and Gauge
In model railroading "scale" is the relationship between the size of a model and an actual train. "Gauge" is the distance between a track's rails. Model railroading products are most readily available in O, HO, N, and Z scales. In model railroading people sometimes use the terms gauge and scale interchangeably.
Scale and gauge values may vary slightly in different countries. Values on this page may have been rounded off. Most manufacturers offer products in more than one scale. On this page manufacturers have been listed under only one of the scales that they offer.
Railroad Track Gauge
In North America "standard gauge" track is spaced 4'8" (1,422.4 mm) between the rails. However, in the early years of railroading there were many "narrow gauge" railroads that used track spaced at 3' (1 yard). Narrow gauge modeling will be covered on a separate page.
You would calculate the standard gauge for HO scale by dividing 1,422.4mm by 87. Your result, 16.35mm is very close to the 16.5mm value listed below. If you do the math, you'll notice that not all the gauges listed below are "in scale". 3-Rail O scale and OO scale are notably out of scale.
G Scale: 1:24th
Gauge: 1.75” (45mm)
G, or "garden is the largest consumer scale. Because of its size it is frequently used outdoors. However, Lionel makes a very nice, affordable G Scale Christmas set for under your tree.
O Scale (3-Rail): 1/48th
Gauge: 1.25” (32mm)
3-Rail O scale model trains were introduced by Lionel about a century ago. The 1/48th scale was chosen because it was the most popular scale for doll houses of the day.
S Scale: 1/64th
Gauge: 1” (26mm)[/br]
This scale was introduced by American Flyer after WWII. Few companies manufacture S scale today; American Flyer still exists, but as one of the Lionel companies.
OO Scale: 1:76.2th
Gauge: 0.65” (16.5mm)
OO scale is the most popular scale in the UK, the British firm Hornby being its largest manufacturer. It uses the same gauge track as HO scale, but trains are slightly larger, making their wheels slightly out of scale
HO Scale: 1:87th
Gauge: 0.65” (16.5mm)
The most popular scale worldwide. HO boasts the widest range of products from the greatest number of manufacturers.
TT Scale: 1:120th
Gauge: 0.47”(12mm)
Popular in Russia and other countries of the former Soviet Union.
N Scale: 1:160th
Gauge: 0.35” (9mm)
"N" short for nine millimeter is the second most popular scale worldwide. This scale allows more complex layouts in available space.
Z Scale: 1:220th
Gauge: 0.26” (6.5mm)
The smallest commercially available scale, it is popular with apartment dwellers and others with very limited space for a layout. Some Z scale manufacturers even offer briefcase layouts, entire layouts with landscape and a town in a briefcase case. These are high-end executive toys that sell for over $1,000.
As you can see, there is a wide range of options when it comes to choosing your scale.