LC Resonant Frequency and Reactance Calculator
Find the resonant frequency of an LC circuit and the reactance of each part at any frequency.
How it changes with frequency
Formulas
f0 = 1 / (2π√(LC)). At resonance the inductive reactance XL = 2πfL equals the capacitive reactance XC = 1/(2πfC). Below resonance the capacitor dominates, and above it the inductor does.
Frequently asked questions
What is LC resonance used for?
Tuning radio receivers and oscillators, picking out a single frequency, and wireless charging coils. At resonance a series LC circuit has its lowest impedance and a parallel LC circuit has its highest.
Why does my measured resonance differ from the calculation?
Real parts have tolerance, and the board and leads add stray capacitance and inductance. The effect grows at higher frequencies.