Q Factor Calculator

Calculate the Quality Factor of a coil or capacitor with the Q Factor Calculator and learn on the go 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

Units: You can choose your preferred units of measurement through selecting the units cells and clicking the arrow to display a list of available options

Learn As You Go: This feature displays a live example of how to calculate Q Factor using the figures that you enter

Reference: ARRL – The Radio Amateur’s Handbook