Calculate impedance, reactance balance, phase angle, power factor, resonance frequency, and optional current or power for series or parallel RLC networks.
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Basic circuits
An RLC impedance calculator is most useful when you need to understand both magnitude and behaviour, not just one reactance value in isolation. This version compares series and parallel RLC networks at the chosen frequency, then adds phase, power-factor, resonance, and optional current or power context from an entered supply voltage.
This page takes one resistance, one inductance, one capacitance, and one operating frequency, then solves the equivalent impedance of either a series or parallel RLC network.
That makes it useful for AC design checks, resonance intuition, and first-pass troubleshooting where you need to see whether inductive or capacitive behaviour dominates at the stated frequency.
In a series RLC branch the resistance and net reactance combine directly into one impedance triangle, so the impedance magnitude follows from resistance and reactance together.
In a parallel RLC branch the calculation works through admittance instead. Conductance comes from the resistor branch, susceptance comes from the inductor and capacitor branches, and the equivalent impedance is the reciprocal of the resulting admittance magnitude.
X_L = 2πfL; X_C = 1 / (2πfC)
Inductive reactance rises with frequency, while capacitive reactance falls with frequency.
Z_series = √(R² + (X_L - X_C)²)
Series impedance comes from the resistor and the net reactance at the operating frequency.
Y_parallel = √(G² + B²); Z_parallel = 1 / Y_parallel
Parallel impedance is found from conductance and susceptance rather than direct resistance-plus-reactance addition.
The resonant frequency is the point where the inductor and capacitor balance each other in magnitude. At that frequency the reactive terms cancel in the ideal series case, and the circuit moves closest to purely resistive behaviour.
Comparing the entered operating frequency with resonance helps explain the reported phase angle and power factor. Below resonance the circuit is more capacitive, while above resonance it becomes more inductive.
f₀ = 1 / (2π√(LC))
The standard resonance equation shows where inductive and capacitive effects balance for the stated L and C values.
This calculator treats the network as an ideal single-resistor, single-inductor, single-capacitor AC model. It does not estimate component tolerance, inductor resistance, capacitor ESR, saturation, dielectric loss, skin effect, or source impedance.
Use it as a planning and educational reference. If the design is sensitive to losses, thermal limits, control stability, or high-frequency parasitics, move to the model or measurement method that captures those effects explicitly.
Frequently asked questions
Because the sign depends on whether inductive or capacitive behaviour dominates at the chosen frequency. Inductive dominance produces a lagging phase angle, while capacitive dominance produces a leading one.
Because resonance explains where the reactive terms balance. Knowing how close the operating frequency is to resonance helps you understand whether the network will look more resistive, inductive, or capacitive.
Only as a first-pass estimate. Real RLC circuits also depend on winding resistance, capacitor losses, source loading, stray capacitance, and frequency-dependent parasitics that this ideal model does not include.
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