About this calculator
Capacitors combine the opposite way to resistors. In parallel (side by side) their plate areas effectively add, so the capacitances simply add. In series (end to end) the total is lower than the smallest one, found from the sum of reciprocals. Enter two to six values; leave unused boxes empty. You can mix units — for example µF and nF.
Formula
Parallel: Ctotal = C1 + C2 + … + Cn
Series: 1 ÷ Ctotal = 1 ÷ C1 + 1 ÷ C2 + … + 1 ÷ Cn
For two capacitors in series: C = C1C2 ÷ (C1 + C2). 1 µF = 1000 nF = 1 000 000 pF.
Worked example
10 µF, 22 µF and 47 µF:
- Parallel: 10 + 22 + 47 = 79 µF
- Series: 1 ÷ (0.1 + 0.045455 + 0.021277) = 1 ÷ 0.166731 = 5.998 µF
Two equal 100 nF capacitors in series give exactly half: 50 nF.
Assumptions and limitations
- Ideal capacitors at their nominal values. Real capacitors have a tolerance, often ±5% to ±20% (electrolytics can be wider).
- In series, the voltage does not always share equally between capacitors — leakage differences can put most of it across one. Check every capacitor’s voltage rating; balancing resistors are often used.
- A zero value is not accepted: it is not a meaningful capacitor in parallel, and it makes the series formula undefined.
References
- Series and parallel capacitance formulas from charge conservation and Kirchhoff’s voltage law.