Here is the formula I couldn't quite remember, besides L and C, the square of the frequency is also involved: L * C * f * f = 25330 In the formula above:
f is the frequency in megahertz
C the capacitance in pico farads
L the inductance in micro henries.
25330 will always be the same in every calculation.
Inductance times capacitance times frequency times frequency will always equal 25330.
Some call it magic. Okay, we're really talking simplicity.
Using this formula, it's also very easy to change the operands around to calculate any one of the values, when the others are known.
Solving for Inductance (in µH): L = 25330 / (C * f * f)
Solving for Capacitance (in pF): C = 25330 / (L * f * f)
Solving for Frequency (in MHz): f = Sqrt(25330 / (L * C))