Javascript® Electronic Notebook Coil Inductance Calculator by Martin E. Meserve

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This page contains two inductor calculators. With both calculators, the main limitation is that they be Single-Layer Air-Core inductors. The first one, below, uses formula published in the ARRL Handbook For Radio Amateurs, and many others. It's nice because it requires only a few inputs to get a estimate of the inductor.

Both calculators come up with inductance estimates that are very close. The second method, however, provides more information, like Reactance, Q, and Self Resonant Frequency.

This is a very simple calculator for estimating the inductance of a Single-Layer Air-Core inductor. The program uses formula published in the ARRL Handbook For Radio Amateurs and other radio publications.

In the text areas provided, enter the Coil Diameter, Coil Length, and Number Of Turns. You can use either inches or millimeters and you can mix and match. The estimated Inductance, in uh, and Coil Turns Spacing will be calculated. Recalculation is automatic. Just click outside the entry area after changing any input data.

The formula is correct to 1%, provided that L > 0.8 × D/2, i.e. the coil is not too short.

If you need a more accurate reading, or the coil does not meet the Single-Layer Air-Core coil criteria, use an Inductance Bridge or Grid-Dip Meter to determine the inductance.

This calculator, takes into account the wire size and wire composition. It was addressed by Serge Stroobandt, ON4AA on http://hamwaves.com/antennas/inductance.html. Please refer to that site for detailed information. I only reconfigured it a bit to make it easier to use.

The table below lists some of the results from intermediate calculations and the final output. Of particular interest might be the Effective Wire Length. That value would be useful when you are creating a shortened dipole or a multiband dipole. For a shortened dipole, the Effective Wire Length indicates the reduction in length, for the wire past the inductor.