Q Factor Calculator

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Calculate resonant frequency, Q factor, bandwidth, and reactance for ideal series or parallel RLC circuits and inductor/capacitor loss analysis.

Input Parameters

Circuit Type

Choose the Q model.

Inductance L

µH

Inductance value.

Capacitance C

Capacitance value.

Resistance R

Series resistance for series mode; parallel resistance for parallel mode.

Operating Frequency

MHz

Optional comparison frequency.

Results

Resonant Frequency

Q Factor

Bandwidth

Reactance at f0

Q at Operating Frequency

Design Note

Equations Used

Resonant Frequency: f₀ = 1 / (2π√(LC))

Series RLC Q: Q = (1/R) × √(L/C) = ω₀L / R

Parallel RLC Q: Q = R × √(C/L) = R / (ω₀L)

Bandwidth: BW = f₀ / Q

Reactance: X_L = 2πf₀L

Frequently Asked Questions (FAQ)

Q1: What is Q factor?
Q factor indicates how selective or low-loss a resonant circuit is. Higher Q means narrower bandwidth and lower damping.

Q2: How is Q different for series and parallel circuits?
Series Q uses series resistance as loss, while parallel Q uses parallel resistance as loss. The formulas are different.

Q3: What does bandwidth mean here?
For an ideal resonant circuit, bandwidth is resonant frequency divided by Q.

Q4: Can this be used for inductors?
Yes, if you know equivalent series resistance and operating frequency. Real inductor Q is frequency-dependent.

Q5: Why is real Q different from calculated Q?
Parasitics, core loss, ESR, skin effect, dielectric loss, and layout all affect measured Q.

Q6: Is higher Q always better?
Not always. High Q improves selectivity but can increase ringing, settling time, and sensitivity to tolerance.

Disclaimer: This calculator uses ideal RLC equations. Real Q depends on ESR, core loss, dielectric loss, skin effect, self-resonance, PCB layout, temperature, and measurement conditions.

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