RLC Resonant Frequency Calculator

RLC resonant frequency Calculator provides an automatic solution for calculating resonance frequency provided that value of capacitance and inductance are known.

The above calculator can be used for calculating Series and Parallel resonant frequencies, Series Damping Factors and Parallel Damping Factors.

The electrical resonant circuit is a combination of LC (R may be included sometimes). The resonance frequency in any circuit occurs when the imaginary parts of impedances cancel each other.

Mathematical Formula and Derivation

The value of resonant frequency can be calculated from the values of L and C. To derive this equation let’s consider the capacitance and inductive reactance:

Capacitive reactance: XC = 1/2πfC
XL = 2πfL

At resonance both are equal:

2πfL = 1/2πfC


f = 1/2π√LC

which is the final derivation.

Theory of Resonance Frequency

A resonant circuit contains an inductor, a capacitor and resistor (presence is not compulsory) which connects with a current or voltage source.

Series Resonance

The simple series circuit contains a capacitor, an inductor and sometimes a resistor. The ac voltage source connects with these components.

Since this is an ac circuit, the overall impedance is:
ZT = R + jXL – jXC (Capacitive reactance uses negative sign)



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