Last updated: 2026-06-15

Series and parallel capacitors

Capacitors combine in the opposite way to resistors. Placing them side by side across the same two points (parallel) adds their capacitances, while stacking them in a line (series) reduces the total. This calculator reports both totals at once for any number of capacitors.

Parallel: capacitances add

Capacitors in parallel share the same voltage, and their capacitances add:

Connecting capacitors across the same nodes is like enlarging the plate area, so the total is always larger than the biggest single capacitor. Two $100\ \mu\text{F}$ capacitors in parallel make $200\ \mu\text{F}$.

Series: reciprocals add

Capacitors in series carry the same charge, and the reciprocals of their capacitances add:

so

Stacking capacitors is like increasing the plate separation, which lowers capacitance. The total is always smaller than the smallest single capacitor. Two $100\ \mu\text{F}$ capacitors in series make $50\ \mu\text{F}$.

Worked example

Three capacitors of $100\ \text{pF}$, $200\ \text{pF}$ and $300\ \text{pF}$:

Why capacitors are the mirror of resistors

Capacitance is proportional to plate area and inversely proportional to plate spacing. Parallel connection effectively adds area, so capacitances add — the same rule that resistors follow in series. Series connection effectively adds spacing, so capacitances combine through reciprocals — the rule resistors follow in parallel. Keeping that mirror image in mind avoids a common mix-up.

Why use capacitors in series

Series capacitors split the applied voltage between them, so each handles only a fraction of the total. A string of capacitors can therefore withstand a higher voltage than any single unit is rated for, at the cost of reduced overall capacitance. Series connection is also a way to obtain a value that no standard single capacitor provides.

Limitations

The formulas assume ideal capacitors. In a series string the voltage divides in inverse proportion to capacitance, so mismatched capacitors or differing leakage can leave one unit overstressed; in practice balancing resistors are often added. Real capacitors also carry a tolerance and a maximum voltage rating that must be checked separately.