Capacitor energy and charge

Calculate ideal stored energy, electric charge and energy available down to a chosen discharge cutoff voltage. Available energy is the difference between initial and cutoff stores. It is not a runtime estimate.

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How it works

Formula

$Initially stored energy = \frac{0.5 \times Capacitance}{1,000,000} \times {Initial voltage}^{2}$
$Energy above cutoff = \frac{0.5 \times Capacitance}{1,000,000} \times ({Initial voltage}^{2} - {Discharge cutoff voltage}^{2})$

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Sources

OpenStax — energy stored in capacitorsSources reviewed: 2026-10-30

Assumptions and limitations

Ideal constant capacitance. Excludes ESR, leakage, tolerance and converter losses. Energy calculations do not establish a safe voltage or discharge procedure; follow component ratings and handling instructions.

How to use this tool

Set up the inputs

Enter capacitance in microfarads, initial voltage and cutoff voltage. The cutoff must be between zero and the initial voltage.

Worked examples

Find the energy stored at 12 volts

1,000 µF = 0.001 F; 0.5 × 0.001 × 12² = 0.072 J; 0.001 × 12 = 0.012 C.

Frequently asked questions

How should I read the result from Capacitor energy and charge?

Initial energy is the full store. Available energy is the difference between initial and cutoff stores; it is not a runtime estimate.

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The calculation or transformation runs in your browser. The tool does not send its input values or generated output to an application server. Loading a page still makes infrastructure requests; optional analytics and Google consent messages have separate controls.

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Consult the linked sources for definitions and reference data. Contact Support if you have a question or notice a problem.

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Capacitor energy and charge

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