Capacitor Energy Calculator
Find the energy stored in a capacitor in joules from capacitance and voltage with this free electronics calculator in your browser.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the capacitance and voltage.
- Press Calculate.
How it works
Stored energy = ½ × capacitance × voltage² (capacitance in farads).
Worked example
1,000 µF at 10 V. = 0.05 J.
Common mistakes
- Using microfarads directly — convert µF to farads (×0.000001) before applying the formula.
- Forgetting that energy scales with voltage squared, so doubling the voltage quadruples the energy.
Frequently asked questions
How much energy does a capacitor store?
E = ½ × C × V², with C in farads and V in volts. A 1000 µF cap at 12 V stores ½ × 0.001 × 144 = 0.072 J.
Why does voltage matter so much?
Energy depends on voltage squared, so a small rise in voltage stores much more energy — and raises the discharge hazard.
What units should I use?
Enter capacitance in farads (1,000 µF = 0.001 F) and voltage in volts; the stored energy comes out in joules.
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Cite this tool
Zerdly. (2026). Capacitor Energy Calculator. Retrieved from https://www.zerdly.com/tools/capacitor-energy-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.