What is an LC resonance calculator?
An LC resonance calculator helps you find the natural resonant behavior of an inductor-capacitor network. In a simple ideal LC tank circuit, energy shifts back and forth between the magnetic field of the inductor and the electric field of the capacitor. At the resonant frequency, this exchange is most efficient.
This tool lets you quickly calculate:
- Resonant frequency (f) from known L and C
- Required inductance (L) from target frequency and capacitor value
- Required capacitance (C) from target frequency and inductor value
Core LC resonance formulas
Primary equation
f = 1 / (2π√(LC))
Where:
- f = resonant frequency in hertz (Hz)
- L = inductance in henries (H)
- C = capacitance in farads (F)
Rearranged for design work
L = 1 / (((2πf)2)C)
C = 1 / (((2πf)2)L)
These are useful when you know your target frequency and need to choose component values.
How to use this calculator
- Select what you want to calculate from the dropdown.
- Enter the two known values.
- Choose the correct units (H/mH/µH/nH, F/µF/nF/pF, Hz/kHz/MHz/GHz).
- Click Calculate to see the result and related values.
The result also includes angular frequency, oscillation period, and equal reactance at resonance.
Practical engineering notes
1) Real components are not ideal
Inductors have series resistance and parasitic capacitance. Capacitors have ESR and ESL. Because of this, measured resonance can differ from theoretical calculations.
2) Tolerance matters
If you use a 5% capacitor and a 10% inductor, frequency variation can become significant. For precision filters or oscillators, tighter-tolerance parts are preferred.
3) Layout can shift resonance
At higher frequencies, PCB trace inductance and stray capacitance noticeably change tuned frequency. Keep leads short and use careful grounding and shielding when needed.
4) Q factor and bandwidth
High-Q resonant circuits have narrow bandwidth and stronger selectivity. Lower-Q networks are broader and less selective. Resonance frequency is only one part of final performance.
Typical applications of LC resonance
- RF tuning circuits in radios and communication equipment
- Band-pass and band-stop analog filters
- Oscillator frequency-setting networks
- Inductive wireless power systems
- Sensor front-end and impedance matching circuits
Example use case
Suppose you have a 10 µH inductor and a 100 nF capacitor. Enter those values and calculate frequency. You will get a resonance in the low hundreds of kilohertz range. You can then adjust either component to move resonance to your target band.
FAQ
Does this calculator work for series and parallel LC?
Yes for ideal resonance frequency. Series and parallel topologies differ in impedance behavior and bandwidth, but the ideal resonant frequency expression is the same.
Why are my lab results different?
Likely due to parasitic effects, component tolerances, inductor core behavior, and instrument loading.
Can I use scientific notation?
Yes. Inputs such as 2.2e-6 are supported.