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Degree of Curve Calculator

Description

Prototype railroads often describe how sharp a curve is with a degree of curve, not a radius — the angle a 100ft chord along the curve subtends, a railroad-engineering convention you'll see on historical track charts and prototype plans. It doesn't tell you the radius directly, so this calculator converts between them, then applies your model's scale to give you the matching benchwork radius.

Enter a degree of curve to get the prototype radius (in feet) and your model's equivalent radius. Or switch modes and enter a radius you're already using on your layout to find out what degree of curve it represents in real life — handy for comparing your benchwork against a specific prototype location or era.

Sources

Degree of curve is the standard railroad-engineering 100ft-chord definition: R = 50 / sin(D/2), R in feet. (Highway engineering uses a 100ft arc instead, which gives a slightly different radius for the same degree — this calculator uses the railroad chord convention throughout.) Scale ratios come from the same sources as the Scale Converter:

Disclaimer: scale ratios are generally stable, but always check against your specific manufacturer or national standards body to verify measurements.