Last updated October 5, 2026 · Report an error
A series RLC circuit combines a resistor, inductor, and capacitor, each opposing current flow differently depending on frequency. This calculator finds the circuit's total impedance — the combined opposition to current — at a specific frequency.
How it works
Enter resistance, inductance, capacitance, and the frequency of interest. The calculator computes inductive reactance (XL = 2πfL) and capacitive reactance (XC = 1/(2πfC)), then combines them with resistance using Z = √(R² + (XL − XC)²).
- Enter resistance, R (Ω).
- Enter inductance, L (mH).
- Enter capacitance, C (µF).
- Enter frequency, f (Hz).
- Click Calculate to see your results.
Examples
Near, but not at, resonance
A 100 Ω resistor with a 10 mH inductor and 100 µF capacitor at 100 Hz gives an impedance of about 100.46 Ω — close to pure resistance, since inductive and capacitive reactance nearly (but not exactly) cancel at this frequency.
Who should use it
- Electronics coursework on AC circuit analysis.
- Analyzing filter or resonant circuit behavior at a specific frequency.
Industry applications
- Electronics and RF circuit design
- Radio and communications engineering
Advantages
- Shows the individual reactance components, not just the final impedance.
- Works at any frequency, not just at resonance.
Limitations
- Assumes an ideal series circuit — real components have some additional parasitic resistance/reactance not captured here.
Common mistakes to avoid
- Forgetting that reactance depends on frequency — using the wrong frequency will give a wrong impedance even with correct L and C values.
- Assuming impedance is just R + XL + XC added directly — it combines via the Pythagorean-style formula shown, not simple addition.
Best practices
- Double check units are consistent (mH, µF, Hz) before comparing results across different circuits.
- Use the LC Resonant Frequency Calculator first if you specifically want to find the resonant frequency, rather than checking many frequencies by hand with this tool.
Tips
- Pair this with the Q Factor Calculator to understand both the impedance and the sharpness of resonance for the same RLC circuit.