LC Resonant Frequency Calculator
Enter an inductance and a capacitance to find the resonant frequency of an LC tank or series circuit. At resonance the inductive and capacitive reactances are equal, and the circuit responds most strongly at this single frequency.
How to use the resonant frequency calculator
- Enter the inductance in henries (or millihenries, microhenries).
- Enter the capacitance in farads (or microfarads, nanofarads).
- Read the resonant frequency in hertz and the angular frequency in radians per second.
Examples
1 mH and 100 nF
L = 1e-3 H, C = 1e-7 F
f = 15915.49 Hz, omega = 100000 rad/s
1 mH and 1 microfarad
L = 1e-3 H, C = 1e-6 F
f = 5032.92 Hz
Frequently asked questions
What is the LC resonant frequency formula?
The resonant frequency is f = 1 / (2 pi sqrt(L C)), where L is in henries and C is in farads. For 1 mH and 100 nF it is 15915.49 Hz.
What happens at resonance?
At the resonant frequency the inductive reactance equals the capacitive reactance and they cancel. A parallel LC tank shows peak impedance while a series LC shows minimum impedance.
What is the angular frequency?
Angular frequency omega is 2 pi times the frequency, measured in radians per second. It also equals 1 / sqrt(L C) directly.
Does the formula work for both series and parallel LC?
Yes. The ideal resonant frequency is the same for series and parallel LC circuits; only the impedance behaviour at resonance differs.
How do component values change the frequency?
Increasing either L or C lowers the resonant frequency. Because of the square root, multiplying L or C by four halves the frequency.
Related tools
Capacitive Reactance Calculator
Calculate the capacitive reactance Xc of a capacitor at any frequency with Xc = 1 / (2 pi f C). Enter frequency and capacitance to get ohms instantly.
Inductive Reactance Calculator
Calculate the inductive reactance Xl of an inductor at any frequency with Xl = 2 pi f L. Enter frequency and inductance to get the reactance in ohms.
RC Time Constant Calculator
Find the RC time constant from resistance and capacitance, plus charge times and the cutoff frequency. Enter any two of R, C and tau to solve the third.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Battery Life Calculator
Estimate how long a device runs on a battery from its capacity in mAh and current draw in mA. Includes a real-world efficiency factor for an honest figure.
Bernoulli Equation Calculator
Solve Bernoulli's equation for the downstream pressure from density, upstream pressure, two velocities and two elevations for steady incompressible flow.