What is LC resonance?
An LC circuit uses an inductor (L) and a capacitor (C) to store and exchange energy. At a specific frequency, called the resonant frequency, the inductive reactance and capacitive reactance are equal in magnitude and opposite in phase. This frequency is central to radio tuning, filters, oscillators, and impedance matching networks.
Resonant frequency formula
The ideal resonant frequency is:
f0 = 1 / (2π√(LC))
- f0 = resonant frequency in hertz (Hz)
- L = inductance in henries (H)
- C = capacitance in farads (F)
The calculator above converts your input units automatically, then computes:
- Resonant frequency in Hz, kHz, MHz, or GHz
- Angular frequency ω0 in rad/s
- Period T in seconds
How to use this LC circuit resonant frequency calculator
Step 1: Enter inductance
Input your inductor value and select its unit (H, mH, µH, or nH).
Step 2: Enter capacitance
Input your capacitor value and select its unit (F, mF, µF, nF, or pF).
Step 3: Calculate
Click Calculate Resonant Frequency to get the result instantly.
Example calculation
Suppose you have:
- L = 10 µH
- C = 100 pF
Converted to SI units: L = 10×10-6 H, C = 100×10-12 F. Plugging into the formula gives:
f0 ≈ 5.03 MHz
That means the LC network naturally resonates near the 5 MHz range.
Practical design notes
1) Component tolerance matters
Real inductors and capacitors have tolerances (for example ±5% or ±10%). These tolerances shift resonant frequency. In precision designs, use tighter tolerance parts and trim components if necessary.
2) Parasitic effects shift resonance
PCB traces, lead length, and component parasitics add unwanted inductance/capacitance. At high frequency, these effects can be significant. Keep layout compact and verify with measurement tools such as a VNA or impedance analyzer.
3) Losses affect Q factor
The ideal formula assumes no loss. Real ESR, winding resistance, and core losses reduce Q and broaden the resonance peak. If selectivity matters, choose low-loss components.
Series vs parallel resonance
Both series and parallel LC circuits share the same ideal resonant frequency expression, but their impedance behavior differs:
- Series LC: impedance is minimum at resonance.
- Parallel LC: impedance is maximum at resonance.
This difference is why series LC is often used for band-pass behavior and parallel LC for tank circuits and tuned loads.
Where this calculator is useful
- RF front-end tuning
- Band-pass and notch filter design
- Oscillator tank circuits
- Antenna matching and resonant traps
- Educational electronics labs
FAQ
Can I use very large or very small values?
Yes. The calculator supports scientific-scale values through unit conversion and formatting.
Why is my measured resonance different from the calculated value?
Real-world factors such as tolerance, temperature, parasitics, and loading from surrounding circuitry can shift frequency.
Does this include resistance and damping?
No. This tool computes ideal resonance from L and C only. For damped response, include R and analyze Q factor or transfer function.