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LC Resonant Frequency Calculator

Find the resonant frequency of an LC circuit, or solve for the inductance or capacitance, plus the characteristic impedance.

Leave one of the three blank to solve for it. SI prefixes accepted: 100u, 4n7, 1M.
Solved value–
Resonant frequency f₀–
Characteristic impedance √(L/C)–
Angular frequency ω₀–
LCf₀
A parallel LC tank — L and C exchange energy at f₀

LC resonance

An inductor and capacitor together resonate at the frequency where their reactances are equal and cancel. At that point the LC pair stores energy, swapping it back and forth between the magnetic and electric fields.

f₀ = 1 / (2π·√(L·C))

Characteristic impedance: Z₀ = √(L / C)

Rearranged, L = 1 / ((2π·f₀)²·C) and C = 1 / ((2π·f₀)²·L), which is what this calculator solves when you leave L or C blank. Z₀ is the reactance of either component at resonance (Xₗ = X_c = Z₀).

Where it's used

LC resonance sets the tuning of radio filters, oscillators, and matching networks. See the reactance calculatorfor Xₗ and X_c at any frequency, or theRC time constant calculator for first-order RC cutoff.

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