Barry's Coilguns

Inductor Simulation

This is a Java simulation of an air-core inductor. You should see an applet (below) with slider controls to select the coil's dimensions and wire size. (Trouble? See below.) Note this is only the coil and does not include a projectile.

How to Calculate Inductance

This program calculates inductance using Wheeler's Formula:

Equation for Wheeler's Formula

where N = number of turns, A = average coil radius, B = coil length, and C = coil thickness. All dimensions are in inches and the result is microhenries. The simulator handles all necessary conversions to metric and millihenries.

The simulator will incidentally give you other handy information, such as the number of turns and the length of wire needed.

Your goal in this simulator is to design a coil with a certain amount of inductance. You should have already chosen a target inductance value somehow, perhaps by experimenting with the RLC Simulator program. Here you can try various wire sizes and physical dimensions to see what happens. The idea is to design a coil which can be physically built, and which has a reasonably low amount of resistance.

Q. What is a circular mil?
A. Unit of measure used to define the area of a wire. The area of a circle one one-thousandth (0.001) inches in diameter.

Q. Why are the "mm" wire sizes (under the 'Next Wire' button) slightly different than in the results panel?
A. The "mm" wire size is what you would order from a manufacturer. The results panel shows the average diameter of actual wire; it may vary by a few percent from the "mm" size.


This program requires Java Runtime Environment (JRE) 1.4 or above. Please visit to download and install the JRE. Or, if you write Java code then get the software developer's kit (SDK) by following links on Sun's web site.

If my applet still doesn't work, try to open your Java Console window in your web browser. Copy and paste its contents into a message and e-mail it to me for trouble-shooting.

About the Program

The program was written in Java using AWT classes. My Java source code is open and freely available:

Please report bugs, request features, make suggestions and send me compliments about this simulator.

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