Impedance Calculator
Free online Impedance Calculator for AC circuits. Compute series and parallel RLC impedance from resistance, inductance, capacitance, and frequency.
Loading tool...
What is Impedance Calculator?
The Impedance Calculator is a free, browser-based tool that computes the AC impedance of series and parallel RLC circuits. Enter the resistance (R), inductance (L), capacitance (C), and frequency (f), and the tool instantly returns the impedance magnitude |Z|, phase angle φ, complex impedance in rectangular form (R ± jX), and the individual inductive (XL) and capacitive (XC) reactances. It also computes the resonance frequency where XL equals XC. Everything runs entirely in your browser with no data sent anywhere.
Key Benefits
- Supports both series and parallel RLC circuit topologies with a one-click toggle
- Handles a wide range of units — Hz to GHz, H to nH, F to pF, and Ω to MΩ
- Displays magnitude, phase, and complex rectangular form simultaneously for complete analysis
- Shows individual XL and XC reactances so you can see how each component contributes
- 100% client-side and private — no sign-up, no tracking, and works offline
Common Use Cases
- •Electronics engineering — analyze filter circuits, matching networks, and resonant tanks
- •RF and antenna design — compute feedpoint impedance and tune LC matching networks
- •Education and homework — verify AC circuit analysis problems with full formulas shown
- •Power electronics — evaluate impedance at line frequency for power factor correction
- •Audio crossover design — calculate speaker crossover impedance at specific frequencies
How to Use the Impedance Calculator
- Choose a circuit type: Click Series RLC or Parallel RLC to match your circuit topology.
- Enter component values: Type the resistance (R), inductance (L), and capacitance (C) values, selecting the appropriate units for each.
- Set the frequency: Enter the AC frequency in Hz, kHz, MHz, or GHz. The impedance recalculates instantly as you type.
- Read and copy the results: Review the impedance magnitude |Z|, phase angle, complex form, and reactances, then click Copy to save the summary.
Key Features
- Series and parallel RLC circuit impedance with a toggle switch
- Supports Hz/kHz/MHz/GHz, H/mH/µH/nH, F/mF/µF/nF/pF, and Ω/kΩ/MΩ units
- Reports magnitude |Z|, phase angle φ, and complex rectangular form
- Shows inductive reactance XL and capacitive reactance XC separately
- Auto-calculates resonance frequency where XL equals XC
- 100% client-side — no data leaves your device
Frequently Asked Questions
What is the difference between series and parallel RLC impedance?
In a series RLC circuit, the total impedance is Z = R + j(XL − XC), where the reactances subtract directly. In a parallel RLC circuit, the admittances add: 1/Z = 1/R + j(ωC − 1/ωL), so the impedance is computed from the reciprocal of the total admittance. The calculator handles both topologies and switches formulas automatically.
What are XL and XC in the results?
XL is the inductive reactance, calculated as XL = 2πfL in ohms. XC is the capacitive reactance, calculated as XC = 1/(2πfC) in ohms. At the resonance frequency, XL equals XC and the net reactance is zero, making the impedance purely resistive.
How is the phase angle calculated?
The phase angle φ represents the phase shift between voltage and current. For a series circuit, φ = atan((XL − XC) / R). For a parallel circuit, φ = −atan(B / G) where B is the susceptance and G is the conductance. A positive angle means the circuit is inductive (current lags voltage); a negative angle means it is capacitive.
Is the Impedance Calculator free and private?
Yes. The tool runs 100% client-side in your browser — no sign-up, no server calls, and your data never leaves your device. It also works offline once the page is loaded.