Resonant Frequency LC Calculator
Calculate the resonant frequency of an LC inductor-capacitor circuit using f = 1 / (2π√(LC)). Free online calculator with interactive charts, angular frequency, and reactance at resonance.
About This Calculator
The Resonant Frequency LC Calculator computes the natural resonant frequency of an LC circuit (also called a tank circuit or tuned circuit) composed of an inductor (L) and a capacitor (C). This is a fundamental tool for electronics engineers, RF designers, ham radio enthusiasts, and physics students working with oscillators, filters, and wireless communication systems.
The calculator uses the standard formula f = 1 / (2π √(L × C)) where L is the inductance in henries (H) and C is the capacitance in farads (F). It also computes the angular frequency ω = 2πf and the reactance at resonance XL = XC = 2πfL. At the resonant frequency, the inductive and capacitive reactances cancel each other, allowing maximum energy oscillation between the inductor's magnetic field and the capacitor's electric field.
How to use the calculator
Enter the inductance in henries (H) and capacitance in farads (F). You can use scientific notation — for example, 1e-3 for 1 mH (millihenry) or 1e-6 for 1 µF (microfarad). The calculator will instantly compute the resonant frequency in hertz (Hz), angular frequency in radians per second (rad/s), and the reactance at resonance in ohms (Ω).
Applications of LC Circuits
LC circuits are essential in radio frequency (RF) electronics. They are used in AM/FM radio tuners to select specific stations, in LC oscillators to generate stable sine waves, in bandpass and notch filters to pass or block specific frequencies, and in impedance matching networks. In wireless charging, LC resonance enables efficient power transfer between coils. Every radio receiver contains at least one LC circuit that the user tunes to the desired frequency.
Frequently Asked Questions
What is the resonant frequency of an LC circuit?
The resonant frequency of an LC circuit is the frequency at which the inductive reactance equals the capacitive reactance. It is calculated using the formula f = 1 / (2π √(LC)) where L is inductance in henries and C is capacitance in farads. At this frequency the circuit oscillates naturally with maximum amplitude.
How do you calculate the resonant frequency of an LC circuit?
To calculate the resonant frequency enter the inductance in henries H and capacitance in farads F into the formula f = 1 / (2π × √(L × C)). The calculator also outputs the angular frequency ω = 2πf and the reactance at resonance X = 2πfL.
What is an LC circuit used for?
LC circuits also called tank circuits or tuned circuits are used in radio transmitters and receivers for frequency selection bandpass filters oscillators amplifiers tuners and signal generators. They select a specific frequency from a complex signal by resonating at that frequency.
What happens at the resonant frequency of an LC circuit?
At the resonant frequency the inductive reactance equals the capacitive reactance causing the circuit to oscillate with maximum amplitude. The impedance reaches its minimum in a series LC circuit and maximum in a parallel LC circuit. The energy oscillates between the inductor magnetic field and capacitor electric field.
Does the resonant frequency change with resistance?
In an ideal LC circuit with zero resistance the resonant frequency depends only on inductance and capacitance. Real circuits have some resistance which slightly reduces the resonant frequency but the ideal formula f = 1/(2π√(LC)) remains an excellent approximation for high-quality circuits.
What is the difference between resonant frequency and angular frequency?
Resonant frequency f is measured in hertz Hz and represents cycles per second. Angular frequency ω is measured in radians per second rad/s and equals 2π × f. Angular frequency is often used in circuit analysis because it simplifies the equations for inductive reactance XL = ωL and capacitive reactance XC = 1/(ωC).
Can I use this calculator for series and parallel LC circuits?
Yes the resonant frequency formula f = 1/(2π√(LC)) applies to both series and parallel LC circuits. The resonant frequency is the same regardless of the configuration. However the impedance behavior differs series LC has minimum impedance at resonance while parallel LC has maximum impedance at resonance.