Resonant Frequency Calculator

What is LC Resonance?

When an inductor (L) and a capacitor (C) are connected together, they exchange energy back and forth at a specific resonant frequency (f₀). At this frequency, inductive reactance equals capacitive reactance, the circuit's impedance is minimised (series) or maximised (parallel), and the circuit can amplify or select signals.

The Formula

f₀ = 1 / (2π × √(L × C))

Where:

• f₀ = resonant frequency in Hz
• L = inductance in henries
• C = capacitance in farads

How to Use This Calculator

Enter the inductance and capacitance values. The calculator returns the resonant frequency and can also solve for L or C if the target frequency and one component are known.

Practical Examples

Example 1: L = 10mH, C = 100µF. f₀ = 1 / (2π × √(0.01 × 0.0001)) = 1 / (2π × 0.001) = 159.2 Hz.

Example 2: AM radio tuner: L = 250µH, C = 40–400pF (variable). Tune to 530 kHz: C = 1 / (4π² × 530,000² × 0.00025) = 360 pF.

Example 3: RF filter: target 2.4 GHz WiFi. L = 1nH, C = 4.4pF → f₀ ≈ 2.4 GHz.

Applications

LC resonant circuits are at the heart of: radio and TV tuners, oscillators, RF amplifiers, switching power supply output filters, induction heating, wireless power transfer (Qi charging), and metal detectors.