Capacitor Energy Calculator
Calculate energy stored in a capacitor from capacitance and voltage
Stored energy
How we calculated it
About the Capacitor Energy Calculator
A capacitor stores electrical energy in an electric field between its plates. The amount stored depends on capacitance and the square of voltage, so increasing voltage has a much stronger effect than increasing capacitance by the same percentage.
This calculator is useful for electronics, power supplies and energy-storage comparisons, but real capacitors also have voltage ratings, equivalent series resistance and discharge behaviour that a simple energy formula does not capture.
How to Use the Capacitor Energy Calculator
- Enter the capacitance and choose the correct unit, such as microfarads, millifarads or farads.
- Enter the voltage across the capacitor.
- Calculate stored energy and review the result in joules or another supported unit.
- Compare the operating voltage with the capacitor’s rated voltage before using the result in a real circuit.
How the Calculation Works
Stored energy is E = 1/2 CV², where C is capacitance in farads and V is voltage in volts.
The calculator converts capacitance prefixes to farads before squaring voltage and applying the formula. Because voltage is squared, doubling voltage multiplies stored energy by four.
Worked example
Capacitor Energy Calculator Worked Example
1,000 µF capacitor charged to 12 V
1,000 µF = 0.001 F. Energy = 0.5×0.001×12² = 0.0005×144 = 0.072 J.
Result guide
Understanding Your Capacitor Energy Calculator Result
The result is ideal stored electrical energy. Usable delivered energy can be lower because capacitor voltage falls during discharge and losses occur in the circuit.
Before you rely on the answer
Assumptions and Limitations
- The capacitor is adequately modeled as ideal for the energy calculation.
- Capacitance and voltage are measured at the same operating condition.
- Leakage, ESR, dielectric loss and discharge cutoff are excluded.
Practical tip
Using This Result in Practice
Do not exceed the capacitor’s rated voltage simply because the calculated energy looks acceptable. Voltage rating is a hard component limit, not a variable to optimize casually.
Related calculations
Useful Calculations to Continue With
If several capacitors are connected in series, calculate the equivalent capacitance first with the Capacitors in Series Calculator.
If they are connected in parallel, use the Capacitors in Parallel Calculator before calculating stored energy.
Common questions
Capacitor Energy Calculator FAQ
What is the capacitor energy formula?
E=1/2 CV², with capacitance in farads and voltage in volts.
What happens to capacitor energy if voltage doubles?
Energy becomes four times as large because voltage is squared.
Is all stored energy usable?
Not necessarily. Circuit losses and the falling capacitor voltage during discharge can reduce usable delivered energy.