Model trains come in a variety of sizes, or scales, from the very small ones to the larger garden railway variety. Though their sizes were originally described as their “gauge,” scale is now the accepted term. Deciding on a scale is really a matter of personal preference, experience, and budget. There are numerous variations of these scales, but there are five that are the most common, making them the easiest to find. The simplest definition of a model train scale is the relevance of the reduced size to the original train being replicated.
The most common model train scale is HO. HO trains have an approximate ratio to the original train of 1:87. Variations of the HO scale include narrower versions of the same scale, which means the trains are the same scale, but with less space between the tracks’ rails. The HO scale is probably the easiest to find and the easiest to accessorize because many hobbyists use it. It is not so small that creating layouts is complicated, but it is large enough that it shows well.
The N model train scale is probably the second most popular size. N trains are approximately 1:160. The N stands for nine, which is the distance in millimeters between the inside rails of the tracks used in this scale. They are smaller than the more popular HO scale, making them slightly more difficult to accessorize to scale, but the advantage to the N scale is using less space to create a complete layout.
Other common model train scales include O (1:48), G (1:24), and Z (1:220). G scale trains are commonly seen in larger garden railway designs. Z trains are very small, and while a complete layout could be easily achieved in confined spaces, people with large hands, poor eyesight, and physical challenges, such as arthritis, find it most difficult to work with this scale.