Series Capacitance Calculator

Series capacitors — connected end-to-end so the same charge flows through each — produce a total capacitance less than any individual capacitor: 1/C_total = 1/C1 + 1/C2 + 1/C3 + ... This is the dual of series resistors, where resistance adds directly but capacitance follows the reciprocal sum. The reduced total capacitance from series connection is often used intentionally to achieve smaller capacitance values, higher effective voltage ratings, or specific frequency-dependent circuit behaviors.

The physical explanation: in a series capacitor chain, the same charge Q must accumulate on each capacitor. Since C = Q/V, a capacitor with less capacitance requires a higher voltage for the same charge — so smaller capacitors in series take larger voltage shares. The voltage divides inversely proportional to capacitance: V_n = (C_total / C_n) × V_total. A 100 µF and 200 µF capacitor in series with 100 V applied will have 66.7 V across the 100 µF and 33.3 V across the 200 µF capacitor.

The equivalent voltage rating of series capacitors is the sum of individual voltage ratings — assuming the voltage divides proportionally. Two 50 V capacitors in series can theoretically withstand 100 V applied voltage. However, real capacitors have tolerance in both capacitance and leakage resistance, causing unequal voltage sharing. In high-voltage applications, resistors are placed in parallel with each series capacitor (voltage equalizing resistors) to ensure voltage divides equally based on resistance, rather than inversely on capacitance.

Series capacitors are used in: AC coupling (DC blocking) circuits, where the capacitor passes AC signals while blocking DC bias; resonant circuits requiring precise capacitance values; RF matching networks; motor starting capacitors in split-phase motors; and power factor correction systems where the capacitor must withstand higher voltages than a single unit can provide.

In switched-mode power supplies, series capacitors form the tank circuit with inductors in LLC resonant converters. The series capacitor resonates with the transformer leakage inductance at the switching frequency, enabling zero-voltage switching (ZVS) for high efficiency. Precise capacitance values — often achieved by series or parallel combinations of standard values — are critical for proper resonant frequency tuning.

The individual voltage outputs in this calculator allow you to verify that each capacitor in the series chain will not exceed its rated voltage — a critical safety check, especially when using electrolytic capacitors that have strict polarity and voltage limits.