RLC Circuit Calculator
Calculate series and parallel RLC impedance, resonance frequency, Q factor, bandwidth, reactance, phase angle and current for resistor-inductor-capacitor circuits.
📡 Resonance Rule: In an ideal RLC circuit, resonance happens when XL = XC. At that point, f0 = 1 / (2π√LC). Use this with the Reactance Calculator, LC Resonance Calculator, RC Time Constant Calculator and Capacitor Series / Parallel Calculator.
📡 R + L + C → Reactance → Impedance → Resonance
Resistance R
Inductance L
Capacitance C
Frequency
Supply Voltage Optional
Series RLC impedance is Z = R + j(XL − XC). Below resonance it behaves capacitive; above resonance it behaves inductive.
Presets:
Resistance R
Inductance L
Capacitance C
Frequency
Supply Voltage Optional
Parallel RLC is calculated from admittance: Y = 1/R + 1/jXL + 1/(-jXC). Near resonance, impedance becomes maximum for an ideal parallel tank.
Presets:
Resistance R
Inductance L
Capacitance C
Circuit Type
This tab focuses on resonance, Q factor and bandwidth. For a series RLC circuit, Q = ω0L/R. For a parallel RLC tank, Q ≈ R/(ω0L).
Examples:
📐 Formula Reference
Resonance Frequency
f0 = 1 / (2π√LC)
Series Impedance
Z = R + j(XL − XC)
Reactance
XL = 2πfL
XC = 1 / (2πfC)
XC = 1 / (2πfC)
Q Factor and Bandwidth
Qseries = ω0L / R
BW = f0 / Q
BW = f0 / Q
📋 Quick Reference
Frequency Behavior
Below f0capacitive
At f0resonant
Above f0inductive
Series RLC
At resonanceZ minimum
Currentmaximum
Phase≈ 0°
Parallel RLC
At resonanceZ maximum
Supply currentminimum
Tank usetuning
📚 Engineering Notes
Series and parallel resonance differIn series RLC, resonance gives minimum impedance and maximum current. In parallel RLC, ideal resonance gives maximum impedance and minimum supply current.
Q factor controls selectivityHigher Q means a sharper resonance and narrower bandwidth. This is useful in tuned circuits, filters and RF tanks.
Real parts have lossesInductors have winding resistance and capacitors have ESR. These losses reduce Q and shift practical behavior from the ideal result.
Use RMS for AC voltageIf calculating current from impedance, enter RMS voltage for normal AC circuit calculations.
What is an RLC Circuit Calculator?
An RLC circuit calculator helps estimate the behavior of a resistor, inductor and capacitor circuit. It calculates reactance, impedance, resonance frequency, Q factor, bandwidth, current and phase angle.
Series RLC vs Parallel RLC
In a series RLC circuit, all components share the same current and the total impedance is the vector sum of resistance and net reactance. In a parallel RLC circuit, the branches share voltage and the total impedance is calculated from admittance.
When is RLC resonance useful?
RLC resonance is used in tuned circuits, filters, oscillator networks, matching circuits, audio crossover analysis and RF design. Use the LC Resonance Calculator when you only need L-C frequency, and this RLC calculator when resistance, damping and Q matter.
❓ Frequently Asked Questions
Use f0 = 1 / (2π√LC), where L is inductance in henries and C is capacitance in farads.
At resonance, XL and XC cancel each other. The impedance becomes approximately equal to R, phase angle becomes near zero and current becomes maximum.
An ideal parallel RLC circuit has maximum impedance at resonance and draws minimum current from the source. Real losses limit the maximum impedance.
Q factor indicates how sharp or selective the resonance is. Higher Q means narrower bandwidth and stronger peaking around resonance.
Real inductors and capacitors have tolerance, ESR, winding resistance, parasitic capacitance and core losses. These can shift the actual resonance and reduce Q.