Calculator KB-12
Capacitor Combination Calculator
How to get the capacitance you need and what voltage each capacitor will have to withstand.
Result
In brief: Calculate capacitance for series and parallel capacitor combinations: total capacitance, voltage distribution, charge, and energy. Example: Total capacitance: 6.875 µF.
Calculation example
| Capacitors separated by spaces | 10u 22u |
|---|---|
| Connection | Series |
| Voltage across the combination | 12 V |
| Total capacitance | 6.875 µF |
|---|---|
| In series | 6.875 µF |
| In parallel | 32 µF |
| Charge | 82.5 µC |
| Stored energy | 495 µJ |
How it is calculated
Series: 1/C = 1/C₁ + 1/C₂ + …
Ui = Q / Ci
In parallel, capacitances add up, but the voltage rating is limited by the weakest capacitor. In series, capacitance decreases, but the voltage is divided between the capacitors in inverse proportion to their capacitance.
What to look for
- Use balancing resistors with electrolytic capacitors in series: differences in leakage current can cause the voltage to divide unevenly.
- Several capacitors in parallel reduce ESR and handle ripple current better than a single large capacitor.
Frequently asked questions
How is capacitance calculated for parallel and series connections?
Capacitances add in parallel: 10 µF and 22 µF give 32 µF. In series, their reciprocals add: the same capacitors give 6.875 µF.
What voltage will be across each capacitor in a series connection?
The smaller capacitor has the higher voltage across it: U₁ = U · C₂ / (C₁ + C₂). With 12 V across 10 µF and 22 µF capacitors, the voltages will be 8.25 V and 3.75 V.
Why connect capacitors in parallel?
To increase capacitance, reduce ESR, and cover different frequencies: an electrolytic capacitor handles low frequencies, while a ceramic one handles high frequencies. The pack’s voltage rating is limited by the lowest-rated capacitor.
