Resonant LC Frequency Calculator
Enter inductance and capacitance to calculate resonant frequency (f0), angular frequency, period, and reactance at resonance.
where L is inductance in henries (H) and C is capacitance in farads (F).
An LC circuit is one of the foundational ideas in electronics. It combines an inductor and a capacitor in a way that naturally resonates at a specific frequency. This LC frequency calculator helps you quickly find that resonant point without manually crunching the square roots and unit conversions.
What is LC resonant frequency?
The LC resonant frequency is the frequency where energy oscillates back and forth between the inductor’s magnetic field and the capacitor’s electric field. At this frequency, inductive reactance and capacitive reactance are equal in magnitude:
- XL = 2πfL
- XC = 1/(2πfC)
At resonance, XL = XC, which leads to the familiar equation: f0 = 1 / (2π√(LC)).
How to use this LC frequency calculator
1) Enter inductance
Type your inductor value and choose the correct unit: H, mH, µH, nH, or pH.
2) Enter capacitance
Type your capacitor value and select F, mF, µF, nF, or pF.
3) Click Calculate
The tool returns:
- Resonant frequency in Hz and engineering notation
- Angular frequency (rad/s)
- Oscillation period (seconds)
- Reactance magnitude at resonance
Worked example
Suppose you have L = 10 µH and C = 100 nF. The calculator gives a resonant frequency near 159.15 kHz.
This value is common in RF prototypes, switching filter stages, and educational lab experiments where tuned circuits are needed.
Why LC resonance matters
- Radio tuning: Selects a narrow band around a station’s carrier frequency.
- Filters: Shapes frequency response in analog signal paths.
- Oscillators: Forms the frequency-selective core of many analog oscillator designs.
- Power electronics: Used in resonant converters for efficient switching behavior.
Common mistakes and tips
Unit mismatch
Most errors come from unit conversion issues. For example, entering “10” as H instead of µH changes the result by a factor of one million. Always verify units before calculating.
Ignoring real-world losses
Real inductors and capacitors include ESR, parasitics, and tolerance. So your measured resonant frequency may differ from the ideal calculation. Treat this result as the theoretical center point.
Overlooking component tolerance
A 5% inductor and a 10% capacitor can shift resonance significantly. For precise tuning, choose tighter tolerances and validate on actual hardware.
Quick reference
- Use larger L or C to lower resonant frequency.
- Use smaller L or C to increase resonant frequency.
- At resonance in an ideal LC tank, energy alternates between magnetic and electric storage.
If you want to design a tuned amplifier, RF front-end, or filter network, this LC frequency calculator gives you a fast and reliable starting point.