Capacitor Q Factor Calculator

This tool calculates the Quality Factor of a Capacitor. As the name suggests the higher the numerical value, the better the quality of the component.


Q = 1/(2π*f*C*ESR)


  • f = Frequency
  • C = Capacitance
  • ESR = Equivalent Series Resistance

The Dissipation Factor DF = 1/Q.


The quality factor Q, is a dimensionless number that is equal to the capacitor’s reactance divided by the capacitor’s equivalent series resistance (ESR).


An ideal capacitor has an ESR = 0. In that case Q = ∞. However in practice the series resistance is never zero. Ideally this value is kept as small as possible to minimize losses.

Typical quality factor values of a Capacitor advertised as having High Q are shown below.

Using the calculator above, a capacitance of 1000 pF, Frequency 1 kHz and ESR of around 16 Ω gives a Q = 10,000.

Example Calculation

A capacitor with an ESR of 0.2 Ω, capacitance 10 μF and Frequency 120 Hz has a Quality Factor Q=663.