# 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.

## Formula

Q = 1/(2π*f*C*ESR)

where,

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

The Dissipation Factor DF = 1/Q.

## Background

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).

Q = XC/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.

The picture below shows Q vs Capacitance of a 1000 pF capacitor intended for RF applications.

For a fixed value of capacitance:

• Q decreases with increasing frequency
• ESR increases with frequency.

## Example Calculation

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

## Summary

The Quality Factor (Q) of a Capacitor refers to its ability to store and release energy efficiently.

It is a measure of the ratio between the maximum energy stored in the capacitor and the energy dissipated per cycle.

Q is determined by various factors such as the capacitance, reactance, and operating frequency of the circuit. A higher Q signifies a more efficient capacitor. In an ideal capacitor, Q would be infinite, meaning that no energy is dissipated during operation.

However, in practical capacitors, energy dissipation is inevitable due to factors such as internal resistance and dielectric losses.

## Book Recommendation

Interested in learning more about Electronics?

We recommend checking out the Art of Electronics.