LC Resonant Frequency Calculator
Compute the resonant frequency and characteristic impedance of an LC circuit from an inductor and a capacitor.
At resonance the inductive and capacitive reactances cancel. Used to set the frequency of oscillators, RF tanks and filters.
Disclaimer: This calculator is provided for general informational and educational purposes only, on an “as is” basis and without any warranty of accuracy or fitness for a particular purpose. Results may contain errors — always verify independently before relying on them in real designs. PartAndStock accepts no liability for any loss or damage arising from use of this tool, including when embedded on third-party sites.
How to use
- 1Enter the inductor's inductance in µH.
- 2Enter the capacitor's capacitance in nF.
- 3The resonant frequency and characteristic impedance are computed instantly.
How it works
Enter the inductance (L) and capacitance (C) to instantly find the LC tank circuit's resonant frequency and characteristic impedance.
How resonance happens
When an inductor and capacitor are connected together, at one frequency the inductive reactance (XL = 2πfL) equals and opposes the capacitive reactance (Xc = 1/2πfC), and they cancel. That is the resonant frequency: f = 1/(2π√(LC)). At resonance, energy sloshes back and forth between the inductor and capacitor.
Where it's used
LC resonance tunes stations in radios, sets frequency in oscillators, and does filtering and impedance matching in power electronics. A series LC shows minimum impedance at resonance; a parallel (tank) LC shows maximum impedance. The characteristic impedance Z₀ = √(L/C) matters for the circuit's quality factor and bandwidth.
Worked examples
- L=100 µH, C=100 nF → f = 1/(2π√(100µ·100n)) ≈ 50.3 kHz
- L=10 µH, C=100 pF → f ≈ 5.03 MHz
- L=100 µH, C=100 nF → Z₀ = √(L/C) ≈ 31.6 Ω
Common LC Values
| L | C | f (approx.) |
|---|---|---|
| 100 µH | 100 nF | 50.3 kHz |
| 100 µH | 1 nF | 503 kHz |
| 10 µH | 100 pF | 5.03 MHz |
| 1 µH | 100 pF | 15.9 MHz |
| 10 mH | 10 nF | 15.9 kHz |