How To Build a Model Railroad Choosing model rail sizes for your HO and N scale layout

Choosing model rail sizes for your HO and N scale layout

By Jeff Wilson | March 1, 2023

Breaking the “code”

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Image showing profiles of model train rail


Choosing model rail sizes is one of the things modelers often spend time on when building their second layout. We often start with whatever came in the train set we began with, but then we start to hear about rail “codes,” and how they can differ.

Regardless of scale, model rail sizes are specified by code. This isn’t a top-secret formula: code simply refers to the height of the rail in thousandths of an inch. Thus code 83 track has rail .083″ tall, code 70 is .070″ tall, and so on. These charts will help you with choosing model rail sizes.

Image showing profiles of model train rail
The accompanying chart lists common model rail sizes in each scale, along with the corresponding prototype rail each represents. Use this for help in choosing model rail sizes.

On the prototype, rail size is measured not by height, but by weight. Rail is classified by the weight in pounds of one yard (36 inches) of rail. Note that some model track scales out to be extremely heavy (code 100 in HO is oversize for almost all prototype rail; code 80 in N is grossly oversize for all prototypes). The heavier rail is easier to work with, and sturdier, which is why it’s often included in train set packages. Extremely light rail can make spurs and seldom-used tracks look more realistic, but because of their fragility, can be difficult to install.

Image shows early rail cross sections from 1808 to 1865
Many styles of iron rail were tried before modern steel T-rail appeared in the mid-1860s. Bethlehem Steel Co.

Using different sizes is a good way to differentiate the apparent purpose of model track: for example, in HO, using code 83 for the main line and code 70 for spurs and sidings.

Image shows rail profile comparing small 90-pound rail with large 132-pound rail superimposed on one another
Rail height varies by weight. The shaded rail is 90-pound ARA-A rail (5-3/8″) and the tall rail is 132-pound RE rail (7-1/8″), which is also about an inch wider at the base. American Railway Association


One thought on “Choosing model rail sizes for your HO and N scale layout

  1. I’m building an additional 3′ x 6′ section of town adjacent to my existing HO layout. It will include only a streetcar line with 6.5 inch curves for my Bachmann PCC streetcar. The track will be embedded in the streets. What code track do you recommend?
    David Z., Scottsdale, AZ

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