Series and Parallel Capacitor Calculator (Equivalent Capacitance)

How do capacitors combine?

Capacitors follow the opposite rule to resistors. Connecting them in parallel is like enlarging the plate area, so capacitances add. Connecting them in series is like widening the gap between the plates, so the equivalent gets smaller.

Parallel

C_eq = C1 + C2 + … + Cn

Every capacitor sees the same voltage. The result is larger than the largest capacitor.

Series

1 / C_eq = 1 / C1 + 1 / C2 + … + 1 / Cn

Every capacitor holds the same charge. The result is smaller than the smallest capacitor. For two capacitors the shortcut is C1 × C2 / (C1 + C2).

Example

10 µF, 22 µF and 47 µF in parallel give 79 µF. The same three in series give 1/10 + 1/22 + 1/47 = 0.1667, so the equivalent is 6.0 µF.

Voltage sharing in series

The voltage does not split evenly across series capacitors. Because the charge is common, the smaller capacitance ends up with the higher voltage. When capacitors are put in series to raise the voltage rating, check the voltage on each part and use balancing resistors on DC.

Charge and energy

When a voltage is entered the tool also gives the stored charge (Q = C × V) and energy (E = ½ × C × V²). A charged capacitor can hold a dangerous voltage after the supply is removed.