Impedance Calculator

Calculate the impedance of an AC circuit with the Impedance Calculator, and learn how with the integrated live example

The DC resistance of a length of wire may be very small, but the effective resistance can be very high when the length of wire is powered with an AC signal. This is called the impedance.

The formula to calculate impedance is:

$Z=\sqrt{R^2 + X^2}$

Where
Z = Impedance in ohms
R = Resistance in ohms
X = The total reactance in ohms = X_L – X_C

Example: Find the impedance of a coil with a wire resistance of 2.3 ohms and reactance of 5000 ohms

$Z=\sqrt{2.3^2+5000^2}=\sqrt{5.29+25000000}$

$=\sqrt{25000005.29}$

$Z=5000.001\; ohms$

Using the Impedance Calculator

Resistance: Input the resistance and select your preferred units

Reactance: Input the total reactance and select your preferred units

How To Calculate Impedance: This feature displays a live example of how to calculate impedance using the figures that you enter

The result is calculated and updated automatically as you enter different numbers or change between the input fields. If the calculated result hasn’t updated after you’ve finished entering your values, click or tap on the result.

Reference: ARRL – The Radio Amateur’s Handbook