Calculating Switch
Frog and Rail Dimensions

The frog number of a switch is defined as the ratio of distance from the where the routes join to the point where the diverging rail crosses the centerline of the non-diverging track.

Note: All Tie Length Calculators now have Frog Calculations


(Hit the "Back" button to go back to the main page.)

This program calculates the frog number you need for a switch based on the turning radius of the diverging branch, as well as the frog angle and the lengths of the point rails. 

Explanation of Input Boxes


Note: All dimensional units must be the same. Inches, meters, etc.

Radius of Diverging Branch

  There are two boxes here. One for the radius and one for an optional
  multiplier. The multiplier can be used to convert feet to inches,
  meters to centimeters, metric to english, or whatever you like.

Track Gauge

  You can enter your actual gauge here. Or you can add the width of the
  rail head. This will give you results based on rail centerlines.

Calculator Resolution

  This allows you to select how much precision you need. The frog number
  will be rounded to the nearest unit you select here.
Switch Frog and Rail Calculator

 x Radius of Diverging Branch
  Track gauge
  Calculator Resolution
  Straight Point Length
  Curved Point Length
  Frog Angle (degrees)
  Frog Number