Capacitor Network Combiner

Build any series, parallel or mixed capacitor network and read the equivalent capacitance as you type. Click a value to edit it, switch any row between series and parallel, and see the schematic redraw — with the rules the opposite way round from resistors.

Capacitor network

C1FIRST
C2
C3

Supply voltageV

Equivalent capacitance

C_eq =99.69 nF2 groups · caps SWAP series / parallel rules vs resistors

Everything you know about resistors, backwards

Capacitors in parallel add; capacitors in series combine by reciprocal sum. That is the exact reverse of resistors, and it catches almost everyone at least once. The reason is geometric: putting capacitors side by side is like widening the plates, so capacitance grows. Stacking them in series is like moving the plates further apart, so capacitance falls.

Why series capacitors store less, not more

In series the same charge has to sit on every capacitor, but the voltages add up. More volts for the same charge is, by definition, less capacitance — C = Q/V. Two 10 µF capacitors in series give 5 µF, and the result is always smaller than the smallest member, just as parallel resistors are.

Series splits voltage in inverse proportion

Because the charge is shared, the smaller capacitor takes the larger share of the voltage. A 1 µF in series with a 10 µF across 11 V puts 10 V across the 1 µF and only 1 V across the 10 µF. This is why stacking capacitors to raise the working voltage needs balancing resistors: without them, tolerance spread alone can push one capacitor past its rating.

Learn more → Capacitors — Learn

Quick experiments

Prove parallel adds. Set two capacitors to 10 µF each, both in parallel. The total is 20 µF — straight addition, exactly the rule you would expect from series resistors. This is the half that feels wrong at first.
Prove series halves. Now switch the second to series. The total drops to 5 µF, below the smaller member. Two equal capacitors in series always give exactly half, which is the one series case worth doing in your head.
Watch a small capacitor dominate a series chain. Put 100 nF in series with 10 µF. The total is about 99 nF — the large capacitor barely matters. In series the smallest value sets the result, the mirror of how the smallest resistor dominates a parallel network.
Mix the two in one network. Take the preset 10 µF, 22 µF parallel, then 100 nF in series. The parallel pair combines to 32 µF, then the series 100 nF collapses it to just under 100 nF. Reduce innermost group first, exactly as with resistors.
Build a non-standard value. E-series capacitors come in coarse steps. Two 10 µF in parallel give 20 µF, and three give 30 µF — a practical way to reach a value that is not stocked, and better than one large part for ESR.

Formula reference

Capacitors in parallel: $C_{total} = C_1 + C_2 + \cdots + C_n$
They add — the opposite of resistors.
Capacitors in series: $\frac{1}{C_{total}} = \frac{1}{C_1} + \frac{1}{C_2} + \cdots + \frac{1}{C_n}$
Always smaller than the smallest member.
Two capacitors in series: $C_{total} = \frac{C_1 C_2}{C_1 + C_2}$
Product over sum. Two only.
Voltage across one series capacitor: $V_n = V_{total} \times \frac{C_{total}}{C_n}$
The smallest capacitor takes the biggest share.
Charge and energy stored: $Q = C V \qquad W = \tfrac{1}{2} C V^2$
Energy goes with the square of voltage.

Symbol	Meaning	Unit
$C_{total}$	Equivalent capacitance	F
$Q$	Charge stored	C
$V_n$	Voltage across one capacitor	V
$W$	Stored energy	J

Common mistakes

Using the resistor rules — adding series capacitors and reciprocating parallel ones.
It is exactly backwards. Parallel capacitors add; series capacitors combine by reciprocal sum. Sanity check: if your series answer is bigger than the smallest capacitor, you have used the resistor rule.
Stacking capacitors in series for voltage rating without balancing resistors.
Series capacitors share voltage in inverse proportion to their capacitance, and real parts have wide tolerance — an electrolytic can be −20 %/+80 %. The mismatch puts more than its share across one capacitor. Fit equalising resistors across each.
Assuming the marked value is the actual value.
Class 2 ceramics such as X7R lose capacitance with applied DC bias, sometimes more than half at rated voltage, and electrolytics drift with age and temperature. The combiner works with ideal values; a real network can be well away from them.
Ignoring the working voltage of the equivalent network.
Combining capacitances tells you nothing about voltage rating. In parallel every capacitor sees the full voltage, so the lowest-rated part sets the limit for the whole network.
Reducing a mixed network from the outside in.
Collapse the innermost group first and work outwards, the same discipline as a resistor network. Doing it in the wrong order combines capacitors that are not actually in the relationship you assumed.

Frequently asked questions

How do you calculate capacitors in series?

Add the reciprocals and invert, the same arithmetic as resistors in parallel. Two 10 microfarad capacitors in series give 5 microfarads. The result is always smaller than the smallest capacitor in the chain.

Why are capacitor rules the opposite of resistor rules?

Because capacitance grows with plate area and falls with plate separation. Wiring capacitors in parallel is electrically like widening the plates, so capacitance adds. Wiring them in series is like moving the plates apart, so capacitance falls.

How does voltage divide across capacitors in series?

In inverse proportion to capacitance, because every capacitor carries the same charge. A 1 microfarad in series with a 10 microfarad across 11 volts puts 10 volts across the small one and 1 volt across the large one.

Can I put capacitors in series to get a higher voltage rating?

Only with balancing resistors across each one. Real capacitors have wide tolerance, and an electrolytic can be minus 20 to plus 80 percent, so the voltage will not share evenly and one capacitor can be pushed past its rating.

Does the marked capacitance equal the real capacitance?

Often not. Class 2 ceramics such as X7R lose capacitance under DC bias, sometimes more than half at rated voltage, and electrolytics drift with age and temperature. Calculations assume ideal values, so leave margin.