How to calculate the value of capacitors in parallel?

When you connect capacitors in parallel, you place them side by side. The result is a capacitor with a higher value. In this guide, you'll learn why it works this way, how to calculate the resulting capacitance, and some examples of it in practice. As you'll soon see, it's actually very simple.

How to calculate the value of capacitors in parallel

Calculating capacitors in parallel is pretty easy. You just add up the value of each capacitor. If you want to get fancy, here is the formula:

So if you put a 470 nF capacitor and a 330 nF capacitor in parallel, you'll end up with 800 nF. You can add as many capacitors as you want.

example

Suppose you connect three 1000 μF capacitors in parallel. What is the total capacitance of these three capacitors?

1000 μF + 1000 μF + 1000 μF is 3000 μF. Therefore, the total capacitance of the three capacitors becomes 3000 μF.

Voltage across parallel capacitors

Each capacitor connected in parallel has the same voltage across it. If you know that one capacitor has 5V across it, that means all the other capacitors in parallel with it also have 5V.

Why connect capacitors in parallel?

The most common reason for connecting capacitors in parallel among the hobbyist is simply that you don't have the exact capacitor value you need.

Suppose you want to build a blinking light circuit that flashes at a specific rate. You have calculated that you need a 147 μF capacitor. In the component box, you do not have this value, but you do have 100 μF and 47

μF.

Well, just replace C1 in the above circuit with a 100 μF and 47 μF parallel capacitor, giving you a final total capacitance of 147 μF.

Another typical place you'll see capacitors connected in parallel is in microcontroller circuits. Microcontroller chips typically have multiple power supply pins. It's common to connect a capacitor from each positive supply pin to ground.

Screen shot of microcontroller parallel capacitors

In this case the point is not to get a new capacitor value but to show how many capacitors the circuit needs. Although they are connected in parallel they will be spread across the boards.

Summarize

To get the total value of capacitors in parallel, simply add the values ​​of each capacitor together. For example, one 5 μF capacitor becomes 100 μF. Three 300 nF capacitors become 1 nF.

For simple circuits, they are usually placed in parallel only when a specific value is needed that is not available.