Coil geometry
Diameter, length, turns and inductance are four figures and only three are free, so a published set of all four can fail to close.
Use JavaTC for the arithmetic. Barton B. Anderson's, and it takes the whole geometry at once, primary and secondary and the room around them. It is what this field has checked against itself for years, and this page no longer puts a second set of numbers beside it. Its coupling figure is the one number in it to take as a start and no further, and how to measure that on your own coil is on the calculators index.
What is below is the part JavaTC does not tell you: the range the formula it uses is stated over, and what a tapped primary does to a published set of figures.
solenoid L(µH) = r²N² / (9r + 10l) r, l in inches flat spiral L(µH) = r²N² / (8r + 11w) r mean radius, w radial width
Wheeler 1928, and nothing else. These are the forms the hobby quotes and they are within about one per cent over the shapes a Tesla coil uses. The solenoid form is stated for a coil at least 0.4 diameters long. Below that this page still answers and says on the answer that it is outside the range, rather than quietly being wrong.
A tapped primary: enter the tap, not the winding. The turns in circuit and the diameter those turns reach are what decide the inductance. Checked against three machines out of Barnkob's featured coils and named because they are somebody's work: his own Kaizer DRSSTC II, Franzoli's DRSSTC 3, and Slawinski and Prince's number 6. Entering the whole spiral instead of the tap lands them 21, 30 and 40 per cent low on their published resonance. Their turn spacing is a gap, so the pitch is conductor plus spacing, which their stated outside diameters confirm to under half a millimetre.
Close wound, single layer, air cored. A space wound secondary reads a little low here, and a coil on a ferrite floor is a different problem entirely.
No self capacitance and therefore no frequency. That is the other half of a resonator and it is not Wheeler's. Take it from a measurement or from a modeller, and put both into primary tank or coupled poles.