Capacitor Calculator — Series & Parallel Capacitance

How to use the capacitor calculator — series & parallel capacitance

Enter your capacitor values in microfarads (µF), separated by commas — for example 10, 22, 47. This parallel capacitor calculator instantly returns three results: the parallel equivalent (the simple sum of every value), the series equivalent (always smaller than the smallest capacitor), and the RC time constant for the parallel bank when you supply a resistance. You can mix as many capacitors as you like — the math works the same for two capacitors or twenty. To find the series-and-parallel capacitance of a mixed network, reduce each parallel branch first, then combine those branch totals in series (or the reverse) using the two formulas below.

Formula & explanation

Capacitors in parallel add directly: C_total = C₁ + C₂ + … + Cₙ. Because parallel capacitors share the same voltage, their plate areas effectively combine and the total capacitance grows. Capacitors in series follow the reciprocal rule: 1/C_total = 1/C₁ + 1/C₂ + … + 1/Cₙ, which for just two capacitors simplifies to C_total = (C₁ × C₂) / (C₁ + C₂). Series capacitance is always less than the smallest capacitor in the chain. The RC time constant is τ = R × C (in seconds, with C in farads): after one time constant the capacitor charges to about 63.2% of the supply voltage, and after roughly 5τ it is treated as fully charged.

Examples

Worked example with three capacitors of 10, 22, and 47 µF. In parallel: 10 + 22 + 47 = 79 µF. In series: 1 / (1/10 + 1/22 + 1/47) ≈ 6.00 µF — smaller than the 10 µF capacitor, exactly as expected. Second example, two equal 10 µF capacitors: in parallel they give 20 µF, but in series only 5 µF (equal capacitors in series halve the value). Time constant: that 79 µF parallel bank discharging through a 10 kΩ resistor gives τ = 10 000 × 79×10⁻⁶ ≈ 0.79 s (790 ms) to reach 63% charge.

Frequently asked questions

How do I calculate capacitors in parallel?

Add every capacitance together: C_total = C₁ + C₂ + … + Cₙ. For example, three capacitors of 10, 22, and 47 µF in parallel give 79 µF. Because capacitors in parallel share the same voltage and combine plate area, the parallel total is always larger than any single capacitor. Enter your values above and the parallel result appears instantly.

How do I calculate series and parallel capacitance in one circuit?

Break the network into blocks. Reduce each group of parallel capacitors to a single equivalent with C = ΣC, then combine those equivalents in series using 1/C = Σ(1/C) — or do it in the reverse order for a series-first network. Enter the values for one block at a time here and carry each equivalent into the next step.

Why is parallel capacitance larger than any single capacitor?

Parallel capacitors share the same voltage and their plate areas effectively add together, so total capacitance is the sum of all values.

Why is series capacitance smaller than the smallest capacitor?

In series the charge must flow through each capacitor in turn. The reciprocal formula (1/C_total = Σ 1/Cₙ) means the result is always less than the smallest value.

What is the RC time constant (τ) used for?

τ = RC tells you how quickly a capacitor charges or discharges through a resistor. After one τ the capacitor reaches ~63% of its final voltage; after 5τ it is considered fully charged.

Does capacitor polarity or voltage rating affect these calculations?

No — equivalent capacitance depends only on the capacitance values and how they are wired, so polarity and voltage rating do not change the series/parallel math. They do matter for safe operation: capacitors in series split the applied voltage, so each one sees only a fraction of the total.

What unit should I enter — µF, nF, or pF?

Enter all values in the same unit (µF by default). The results will be in that same unit. If your capacitors are in nF, divide by 1000 to convert to µF first.