Capacitors in Parallel Calculator

Total parallel capacitance, charge on each capacitor and stored energy.

What it does

Capacitors in parallel all see the same voltage, and their capacitances simply add.

Where it's used

Combining bulk and decoupling capacitors, reaching a value you don’t have, and lowering total ESR.

How to use it

Type the values separated by commas.
Enter the voltage.
Optional: set a frequency to see the combined reactance.

The formula explained

C_total: C1 + C2 + … + Cn
Q_n: C_n × V — charge on capacitor n
E: ½CV², total energy stored

Worked example

A typical decoupling bank on a 5 V rail.

Inputs:

Capacitor values (comma separated): 100u, 10u, 100n F
Applied voltage: 5 V
Frequency (reactance): 100k Hz

The calculator gives:

Total capacitance: 110.1 µF
Total charge Q: 550.5 µC
Stored energy: 1.376 mJ

Tips and common mistakes

Every capacitor must be rated for the full voltage.
A large electrolytic plus a small ceramic covers both low and high frequencies.
N identical capacitors in parallel have about 1/N of the ESR of one.

Questions people ask

How much energy does a capacitor bank store?

E = ½ × C × V². The example bank of 110.1 µF on 5 V stores about 1.38 mJ. Energy grows with the square of voltage, so the same bank on 10 V would store four times as much.

Why is my ceramic capacitor smaller than its marking?

Class 2 ceramics such as X5R and X7R lose capacitance as DC voltage is applied — often half or more at their rated voltage, especially in small packages. Check the DC-bias curve in the datasheet before relying on the printed value.

Can I put electrolytic capacitors in parallel for more capacitance?

Yes — it is common in power supplies. Parallel electrolytics also share the ripple current and lower the combined ESR, so they run cooler and last longer than one large part.

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