Capacitor Series/Parallel Calculator
Capacitors behave oppositely to resistors when combined. In parallel, capacitances add directly because the effective plate area increases. In series, the reciprocal rule applies because the effective plate separation increases. This calculator accepts up to 4 capacitor values and computes the total equivalent capacitance. This is essential for filter design, power supply decoupling, timing circuits, and adjusting voltage ratings. Enter values consistently in farads, microfarads (uF), nanofarads (nF), or picofarads (pF).
Capacitor combination formulas
Parallel: C_total = C1 + C2 + C3 + ...
Series: 1/C_total = 1/C1 + 1/C2 + 1/C3 + ...
Note that these rules are the reverse of resistors: parallel capacitors add, while series capacitors follow the reciprocal rule. Two equal capacitors in series give half the capacitance of one; two equal capacitors in parallel give double.
Capacitor circuit design notes
- Parallel capacitors are used in power supply decoupling to reduce impedance across a wide frequency range by combining large electrolytic and small ceramic capacitors.
- Series capacitors are used when no single capacitor with the required voltage rating is available; each capacitor sees only a fraction of the total voltage.
- For AC signal coupling and timing circuits, the total capacitance directly affects cutoff frequency and time constants.
- Always verify voltage ratings, especially in series configurations where unequal ESR can cause uneven voltage distribution.
Frequently asked questions
How do capacitors combine in parallel?
Capacitors in parallel add directly: C_total = C1 + C2 + C3 + ... The voltage across each is the same and the total stored charge is the sum of charges on each capacitor.
How do capacitors combine in series?
For capacitors in series, 1/C_total = 1/C1 + 1/C2 + 1/C3 + ... The charge on each capacitor is the same and the total voltage is the sum of individual voltages.
Why is series capacitance less than the smallest capacitor?
In series, the same charge must be stored across all capacitors. The effective plate separation increases, reducing total capacitance below the smallest individual value.
What units should I enter?
Enter all values in the same unit (farads, microfarads, nanofarads, or picofarads). The result will be in that same unit. For circuit design, microfarads (uF) is most common for larger capacitors.
When would I connect capacitors in series?
Series capacitors are used to reduce total capacitance or to increase the effective voltage rating. For example, two 50 V capacitors in series can handle up to 100 V total, while halving the capacitance.
Official sources
- NIST: NIST SP 811, Guide for SI Units.
- IEEE Standards Association: IEEE Standards.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.