Last updated October 6, 2026 · Report an error
An LC circuit (an inductor and capacitor together) naturally oscillates at a specific resonant frequency, a fundamental building block of radio tuners, filters, and oscillators. This calculator solves for whichever value — inductance, capacitance, or resonant frequency — is missing.
How it works
Enter any 2 of the 3 values (inductance in millihenries, capacitance in microfarads, or resonant frequency in Hz) and leave the one you want to solve for blank. The calculator applies f = 1/(2π√(LC)).
- Enter inductance (mH) — leave blank to solve for this.
- Enter capacitance (µF) — leave blank to solve for this.
- Enter resonant frequency (Hz) — leave blank to solve for this.
- Click Calculate to see your results.
Examples
A simple LC tank circuit
A 10 mH inductor paired with a 100 µF capacitor resonates at about 159.15 Hz.
Who should use it
- Electronics coursework on resonance and filter design.
- Designing radio tuning, filter, or oscillator circuits.
Industry applications
- Electronics and RF circuit design
- Radio and communications engineering
Advantages
- Solves for any of the three variables, not just forward frequency calculation.
- Foundational formula behind tuning, filter, and oscillator circuit design.
Limitations
- Doesn't account for real-world resistance/losses, which affect resonance sharpness (Q factor) though not the frequency itself.
Common mistakes to avoid
- Mixing up millihenries/microfarads with base henries/farads when cross-checking by hand.
- Forgetting that real-world resistance affects how sharp the resonance is (bandwidth), even though it doesn't change this basic frequency formula.
Best practices
- When designing for a target frequency, it's often easier to fix a practical, available capacitor value first and solve for the required inductance (or vice versa).
- Remember this formula gives the idealized resonant frequency — real component tolerances mean an actual built circuit may resonate slightly off from the calculated value.
Tips
- Pair this with the Capacitor Energy and Inductor Energy calculators to understand the full energy behavior of an LC circuit, not just its resonant frequency.
Frequently asked questions
Yes, with no signup and no limit on how many calculations you run.
Energy oscillates back and forth between the inductor's magnetic field and the capacitor's electric field at this specific frequency, with the circuit's impedance behaving very differently right at resonance than at other frequencies — this is the basis for tuning circuits to select one specific frequency.
Radio tuning circuits, band-pass/band-stop filters, and oscillator circuits all rely on choosing L and C values to hit a specific target resonant frequency.
No — this is the idealized formula for a lossless LC circuit. Real circuits have some resistance, which affects how sharply the circuit resonates (its "Q factor") but not the resonant frequency formula itself.