When a problem comes up often enough, I look around and see if someone's made a calculator to automate it. Sometimes, I find one, and put it in the links below. When I can't find one, I create my own:
Bob's Electron Bunker, Multi-Layer Coil Inductance Calculator (possibly more accurate than conventional formulas, but still a long way from a capacitance and eddy current-aware calculator; which alas, might never exist for such configurations)
Coil32.net, a wealth of free online calculators, and a free application (Coil64) collecting them.
Chemandy Electronics, Radio Frequency and Microwave JavaScript Calculator Index, covers many typical structures (microstrip, differential stripline, etc.), and other common electronic and RF calculations. (I suspect the numerical accuracy is better than most. Most calculators use the same old piecewise equations, which produces absurd results for parameters outside the approximation range, which is frequently omitted. These calculators solve the Elliptical and Bessel functions as needed!)
Sourceforge.net, CGI-Wcalc, an impedance calculator toolbox