Impedance Calculator
Impedance of a series resistor, inductor and capacitor at a given frequency — magnitude, phase angle and power factor.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
X = X_L − X_C |Z| = √(R² + X²) φ = arctan(X ÷ R)
Resistance and reactance are 90° apart, so they combine by Pythagoras rather than by adding. The phase angle is what is left over: it tells you how far out of step the current is with the voltage, and its cosine is the power factor.
What to watch out for
Impedance has two parts and they behave differently:
- Resistance dissipates. It turns power into heat and it is the same at every frequency.
- Reactance stores. It opposes current without consuming anything, and it changes with frequency.
Because they are 90° apart they cannot simply be added — 100 Ω of resistance and 100 Ω of reactance gives 141 Ω, not 200 Ω. The phase angle says how much of the total is which: 0° is purely resistive, ±90° is purely reactive.
Frequently Asked Questions
How do you calculate impedance?
|Z| = √(R² + X²), where X is the inductive reactance minus the capacitive. A 100 Ω resistor in series with 62.8 Ω of inductive reactance gives about 118 Ω at a phase angle of 32°.
What does the phase angle mean?
How far the current is out of step with the voltage. Positive means the load is inductive and current lags; negative means capacitive and current leads. Zero means the circuit looks like a plain resistor at that frequency.
What is the difference between impedance and resistance?
Resistance is the part that dissipates power and does not change with frequency. Impedance is the total opposition including reactance, which does change with frequency and stores energy rather than consuming it.