LC Resonant Frequency Calculator
By Santaji GadepatilinUpdated October 27, 2026
An inductor and a capacitor together resonate at one frequency, where their reactances cancel. This is how radios tune to a station and how many oscillators and filters work — see the LC resonant circuit frequency explained. This free LC resonant frequency calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the LC resonant frequency calculator
Enter the inductance in microhenries and the capacitance. The calculator gives the resonant frequency and angular frequency. To design a circuit for a target frequency, enter the frequency and one component and press × on the other.
LC resonant frequency formula
f₀ = 1 ÷ (2π√(LC))
Resonant frequencies
| L | C | f₀ |
|---|---|---|
| 1 µH | 100 pF | 15.915 MHz |
| 10 µH | 100 pF | 5.033 MHz |
| 100 µH | 1 nF | 503.29 kHz |
| 10 µH | 100 nF | 159.15 kHz |
| 1 mH | 1 µF | 5.03 kHz |
| 100 mH | 100 µF | 50.3 Hz |
Series vs parallel resonance
| Series LC | Parallel LC (tank) | |
|---|---|---|
| Impedance at f₀ | Minimum (≈ R) | Maximum |
| Current at f₀ | Maximum | Minimum from source |
| Use | Band-pass in series path, notch filters | Oscillators, tuned amplifiers |
Quality factor
For a series RLC circuit, Q = (1 ÷ R)√(L ÷ C), and bandwidth = f₀ ÷ Q. A higher Q gives a narrower, sharper response — important in radio tuning.
Applications
- AM/FM radio tuning: a variable capacitor changes f₀ to select stations.
- Oscillators: LC tanks set the frequency in many RF circuits.
- Harmonic filters: tuned LC filters remove specific harmonics in power systems.
- Wireless charging: transmitter and receiver coils are tuned to the same resonant frequency.
Frequently asked questions
What is the resonant frequency formula?
f = 1 ÷ (2π√(LC)), with L in henries and C in farads.
What happens at resonance?
Inductive and capacitive reactances are equal and cancel. A series LC circuit has minimum impedance; a parallel LC circuit has maximum impedance.
How do I find the capacitor for a frequency?
Enter the target frequency and inductance, then press × on Capacitance. C = 1 ÷ ((2πf)² L).
What limits real LC circuits?
Resistance in the coil and capacitor losses, described by the quality factor Q. Higher Q gives a sharper resonance.