The scale of a model railroad you build and run is a personal choice based on many factors, but perhaps the most important one is available space. If you have a spare bay in your garage, you can run just about any size of model train. If you are confined to a corner of a spare bedroom, you will be happier with the smaller scales. Other factors, such as budget, fine motor skills, and desired realism play into your decision, too.
What Is Scale?
A full-size Pennsylvania Railroad GG-1 electric locomotive would need 79.5 feet of space in your backyard. An HO version of the same locomotive is 1/87th of that size and would be just under 11 inches long. HO is large enough for modelers of all ages to work with easily, yet it does not take up an entire room.
The N Scale version of a GG-1 would be 1/160th of that 79.5-foot size, or just under 6 inches long. The other popular scales are O (1/48th of actual size), On3 (using HO scale track to make narrow-gauge O scale trains), and Z (1/220th of actual size).
By far the most popular scale, HO has dominated model railroading for generations. Model supply companies provide hundreds of thousands of products in this scale, from houses to scenery to rolling stock and locomotives. An HO scale product is small, but not likely to be lost in the hands of a 7-year-old or a 70-year-old. Scale layouts can fit on a 4 x 8 sheet of plywood.
If manual dexterity, vision or mobility issues are concerns for you, O scale is your ideal choice. Everything about O scale is big, which means you will not lose parts, struggle with getting stock on rails, or need single-hair paint brushes for weathering your structures.
Be careful to differentiate between the O Scale “tinplate” toy equipment (O-27) typically seen at holidays and the O Scale true-scale models. The real scale equipment does not have three rails.
The disadvantage of O scale is the space a modest layout will need. Curves with radii of 72 inches are typical — that is a six-foot sweep, so to have your model train turn around at the end of a layout, you need a minimum of 12 feet!
Using HO track with O scale equipment gives you the narrow-gauge modeling experience of On3. The equipment is the large, easily handled O scale rolling stock and locomotives, but the track radii are much smaller: 36 inches. You sacrifice nothing in realism by opting for the smaller track, as seen in YouTube videos of On3 layouts.
If you have the visual acuity and fine motor skills for N scale model railroading, you can fit a complete layout on your dining table. When your train session is over, it can pack away in a closet if need be. N scale is 1/160th of actual size, so rolling stock fits in your palm; minimum turning radius is under 10 inches; and locomotives are tiny marvels of movement.
With diminishing scales you lose a bit of realism, so N and Z scales will, on close inspection, betray a certain chunky thickness and unrefinement you may not like. For tight spaces, though, they are unbeatable.
At the tiniest end of practical modeling is Z scale (pronounced “Zed scale” in most of the world). Generally a European scale, everything in Z scale is measured in the metric system, so minimum turning radius of 195 mm means around 7.6 inches. This scale is the newest in model railroading, dating only to 1972.
To work effectively in this small scale, you need a steady hand, a keen eye, and plenty of creativity. To get a sense of the tiny Z scale, this YouTube video provides a layout tour with real people next to the smoothly rolling trains.