Series & Parallel Capacitor Calculator

Series and parallel capacitor calculator for equivalent capacitance

When you connect capacitors together, the circuit does not “keep” their individual values. Instead, the group behaves like a single equivalent capacitor. This calculator helps you find that equivalent capacitance for the two most common arrangements: capacitors in series and capacitors in parallel. If you are designing an RC timing circuit, estimating a filter cutoff, building a power supply decoupling network, or just checking whether a parts bin combination will hit a target value, this is the number you need.

The key difference is simple. In parallel, capacitors add directly and the equivalent capacitance increases. In series, the equivalent capacitance decreases, sometimes dramatically, and is usually dominated by the smallest capacitor in the chain. People often remember the series formula for resistors and accidentally apply it to capacitors. This calculator prevents that mistake and shows a clean result in multiple units so you can sanity check your design.

Use it in “quick answer” mode by entering only two values and choosing series or parallel. For more realistic work, enter up to six capacitors and let the calculator ignore any blank fields. The output includes the equivalent capacitance in your chosen unit, plus practical extra context. That context helps you decide if your network is in the right ballpark before you move on to timing constants, frequency response, or component selection.

Assumptions and how to use this calculator

• All entered capacitor values are treated as ideal capacitances at the same operating condition (frequency, temperature, and DC bias effects are not modeled).
• Blank capacitor fields are ignored, so you can enter only the parts you actually have without being blocked.
• Series equivalent capacitance is calculated as 1/Ceq = Σ(1/Ci), and parallel equivalent capacitance is calculated as Ceq = ΣCi.
• Unit conversion uses standard metric prefixes (pF, nF, µF, mF, F) and the calculator returns the result in the selected unit plus common reference units for checking.
• This tool does not estimate voltage rating, ESR, leakage, tolerance stacking, or capacitor balancing requirements (those depend on part type and application).

Common questions

Why does capacitance go down in series but resistors go up?

Capacitors store charge on plates separated by a dielectric. In series, the effective plate separation increases and the same charge must appear on each capacitor, which reduces the group’s ability to store charge for a given voltage. That is why series capacitors behave opposite to series resistors. The math captures this via the reciprocal sum: even one small capacitor can pull the overall equivalent down.

What is the fastest way to sanity check a series capacitor result?

In a series chain, the equivalent capacitance must always be smaller than the smallest capacitor you entered. If your result is larger than the smallest capacitor, something is wrong (usually the wrong mode or a unit mismatch). For two capacitors of similar value, the series equivalent will be roughly half of one capacitor.

What is the fastest way to sanity check a parallel capacitor result?

In parallel, the equivalent capacitance must always be larger than the largest capacitor you entered, because you are adding capacitances. If it is smaller than the largest capacitor, you likely entered a value in the wrong unit (for example nF vs µF) or selected series mode by mistake.

Can I mix different units across capacitors?

This calculator uses one unit selector for all inputs to keep the process fast and reduce mistakes. If your capacitors are labeled in different units, convert them first (for example 0.1 µF = 100 nF). Using a single unit for entry also helps you spot “outlier” values that would otherwise skew the equivalent capacitance.

When does this calculator not apply?

If your capacitors are part of a more complex network (series-parallel combinations with multiple junctions), you may need to reduce the circuit step by step or use circuit analysis tools. Also, for high-frequency or high-current applications, ESR and ESL can dominate behavior. In those cases, equivalent capacitance alone is not enough to predict ripple, impedance, or transient response.