Q Factor Calculator

Calculate the Quality Factor of a coil or capacitor with the Q Factor Calculator, and learn how with the integrated live example

The quality factor of a resonator is related to the bandwidth and is a measure of its resonant frequency response. High Q resonators have a narrow bandwidth so will only respond to and work on a narrow band of frequencies. This makes them more difficult to tune, but they perform better at resonance than low Q resonators. For example, a coil with a high Q value will have greater resonant voltage rise than a low Q coil.

The formula for calculating the Q factor of an inductor or capacitor is:

$Q=\frac{X}{R}$

Where
Q = Quality Factor
X = Reactance in ohms
R = Resistance in ohms

Example 1: Find the Q factor of an inductor that has a inductive reactance of 2400 Ohms and series resistance of 3.5 Ohms

$Q=\frac{2400}{3.5}=685.714$

Example 2: Find the Q factor of a capacitor that has a capacitive reactance of 4000 Ohms and series resistance of 5 Ohms

$Q=\frac{4000}{5}=800$

Use the calculator below to see a live example.

Using the Q Factor Calculator

Reactance: Enter the inductive or capacitive reactance

Resistance: Enter the series resistance

How To Calculate Q Factor: This feature displays a live example of how to calculate Q Factor 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