Scale and Gauge
By Ryan Kunkle, About.com Guide
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.
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 [i]briefcase layouts[/i], entire layouts with landscape and a town in a briefcase case. These are high-end executive toys that sell for over $1,000.
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.
N Scale: 1/160th
Gauge 0.35”; (9mm)
"N" short for nine millimeter is the second most popular scale worldwide. Due to its size this scale is more difficult for modelers to customize than those listed above, but N scale allows more complex layouts in available space.
HO Scale: 1/87th
Gauge 0.65”; (16.5mm)
As the most popular scale worldwide, HO enjoys the widest range of products from the greatest number of manufacturers.