This page lets you do calculations for single layer air cored coils using the solenoid formula:
L (microH) = (r2 n)2) / (9r + 10 l)Here r and l are the coil radius and length in inches and n is the number of turns. Note that strictly r is not the inside radius of the coil, i.e. that of the former, but is measured to the centre line of the winding.
You must specify the diameter of the coil, and its length. You may then either specify the number of turns and calulate the resulting inductance (`Model'), or specify the required inductance and calculate the number of turns (`Design').
Notice that this program does not at present allow you to design a close wound coil directly, although the actual length of winding using the suggested wire gauge is calculated.
Because winding fractional turns is a bit tricky, Design mode will round to the nearest whole turn in the results box, although the fractional number of turns is reported in the large box.
If you click `Model' after `Design' you can calculate the actual inductance with a whole number of turns and allowing for the wire diameter.