Electronics

Capacitor Calculator

Calculate capacitance in series and parallel, RC time constant, and energy stored. Supports multiple capacitor values.

Quick Answer

Series: 1/C_total = 1/C1 + 1/C2 + ... (total is always less than the smallest). Parallel: C_total= C1 + C2 + ... (values add up). RC time constant: τ = R × C.

Mode

Capacitor Values (µF, comma-separated)

Results

59.98 µF

Total (Series)

Capacitors

About This Tool

The Capacitor Calculator handles four common capacitor calculations: series combinations, parallel combinations, RC time constants, and energy storage. Whether you are designing a filter, timing circuit, or power supply, these calculations come up constantly in electronics work.

Capacitors in Series

When capacitors are wired in series, the total capacitance decreases. The formula 1/C_total = 1/C1 + 1/C2 + ... means the result is always smaller than the smallest individual capacitor. Series wiring increases the voltage rating (each capacitor shares the total voltage) but reduces the total capacitance. This is useful when you need a higher voltage rating than any single capacitor can handle.

Capacitors in Parallel

Parallel capacitors simply add together: C_total = C1 + C2 + .... The voltage rating stays the same as the lowest-rated capacitor. Parallel wiring is the most common way to increase total capacitance. In power supply decoupling, you often see a large electrolytic capacitor in parallel with a small ceramic capacitor, combining bulk energy storage with high-frequency noise filtering.

RC Time Constant

The RC time constant τ = R × C tells you how fast a capacitor charges or discharges through a resistor. After one time constant, the capacitor reaches about 63.2% of the final voltage. After five time constants (5τ), it is over 99% charged. The cutoff frequency of an RC low-pass filter is f = 1/(2πRC), where signals above this frequency are attenuated.

Energy Stored

A charged capacitor stores energy equal to E = ½CV². The energy increases with the square of the voltage, so doubling the voltage quadruples the stored energy. This is why high-voltage capacitors can be dangerous even at small capacitance values. Always discharge capacitors safely before working on circuits.

Frequently Asked Questions

When should I wire capacitors in series vs parallel?

Wire in parallel to increase total capacitance (most common). Wire in series when you need a higher voltage rating than a single capacitor provides. Series connection halves the capacitance but doubles the voltage rating for two equal capacitors.

What does the RC time constant mean in practice?

The time constant tells you how long a capacitor takes to charge or discharge. One time constant (tau) means 63.2% charged. Five time constants means over 99% charged. It is used to design timing circuits, filters, and debounce circuits.

How do I read ceramic capacitor codes?

Three-digit codes like 104 mean 10 followed by 4 zeros in picofarads, so 100,000 pF or 100 nF or 0.1 microfarad. The first two digits are significant figures and the third is the multiplier (number of zeros). 473 means 47,000 pF or 47 nF.

Can I mix capacitor types in parallel?

Yes. Mixing types is actually recommended in many applications. A large electrolytic handles low-frequency energy storage while a small ceramic capacitor handles high-frequency noise. The different ESR and frequency characteristics complement each other.

How much energy does a capacitor store?

Energy equals half times capacitance times voltage squared (E = 0.5 * C * V^2). A 1000 microfarad capacitor at 50V stores 1.25 joules. At 400V, the same capacitance stores 80 joules, enough to be lethal. Always respect high-voltage capacitors.

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