Capacitor Energy Calculator
This capacitor energy calculator finds the energy stored in a capacitor from its capacitance and voltage, using the capacitor energy formula. Enter the values and the capacitor energy calculator returns the stored energy in millijoules and joules, plus the charge held.
Results
The Capacitor Energy Calculator is part of our Electronics collection. Browse more electronics to size, convert, and check your work alongside this tool.
What the capacitor energy calculator does
The capacitor energy calculator shows how much energy a capacitor stores in its electric field. That stored energy powers camera flashes, smooths power supplies, and drives motor-start circuits. This capacitor energy calculator uses the capacitor energy formula with capacitance and voltage to return the energy and charge, so you can size capacitors for the job.
Capacitor energy formula
The capacitor energy calculator uses the standard capacitor energy formula, also written as the capacitor stored energy formula:
Because voltage is squared, the energy stored in a capacitor rises fast with voltage. The capacitor energy equation also gives the charge from Q = C × V, which the calculator reports too.
Capacitor energy calculator example
A 1000 microfarad capacitor charged to 12 volts, through the capacitor energy formula:
That is 72 millijoules of energy stored in the capacitor, with 12 millicoulombs of charge.
How to use the capacitor energy calculator
Enter the capacitance in microfarads and the voltage across the capacitor. The capacitor energy calculator applies the capacitor energy formula and returns the stored energy in millijoules and joules, along with the charge in millicoulombs.
Reading the capacitor energy result
The stored energy tells you what the capacitor can deliver in a burst. Double the voltage and the capacitor energy formula gives four times the energy, since voltage is squared. For safety, remember a large charged capacitor holds real energy and must be discharged before handling, a point the calculate-energy-stored-in-a-capacitor result makes concrete.
When to use the capacitor energy calculator
- Sizing a capacitor for energy storage or a flash
- Applying the capacitor energy formula to a power-supply capacitor
- Designing motor-start and pulse circuits
- Assessing the discharge hazard of a large capacitor
Common capacitor energy mistakes
- Forgetting to square voltage. The capacitor energy formula uses V², not V.
- Unit slips. The capacitor energy calculator expects microfarads; convert other units first.
- Underrating the hazard. A charged capacitor stores real energy; discharge it safely.
Tips for accurate capacitor energy results
- Enter capacitance in microfarads as the capacitor energy calculator expects.
- Remember energy scales with the square of voltage in the capacitor energy formula.
- Always discharge large capacitors before handling.
How a capacitor stores energy
The capacitor energy calculator rests on a neat piece of physics. As charge builds on a capacitor's plates, it creates an electric field between them, and energy goes into that field. The relationship is not linear, which is why the capacitor energy formula squares the voltage: the first volt stores a little energy, but each added volt stores more because it stacks on the charge already there. This is the insight behind the capacitor stored energy formula, and it explains why high-voltage capacitors pack so much energy into a small package.
Why the squared term shapes design
Engineers lean on the squared voltage term the capacitor energy formula reveals. To store more energy, raising the voltage beats raising the capacitance, because energy grows with the square of voltage but only linearly with capacitance. That is why camera flashes and defibrillators charge capacitors to hundreds of volts. The same squared relationship in the capacitor energy equation is a safety warning: a capacitor that seems small can hold a dangerous jolt, so calculating energy stored in a capacitor is as much about hazard as design.
Reference Table
| Capacitance | Voltage | Energy |
|---|---|---|
| 1000 µF | 12 V | 72 mJ |
| 1000 µF | 24 V | 288 mJ |
| 4700 µF | 50 V | 5.875 J |
Capacitor Energy Calculator FAQ
What is the capacitor energy formula?
The energy stored in a capacitor is E = ½CV², half the capacitance times voltage squared. The capacitor energy calculator applies this capacitor energy formula, converting microfarads to farads for a result in joules.
How do I calculate energy stored in a capacitor?
Use the capacitor stored energy formula E = ½CV². Enter capacitance and voltage into the capacitor energy calculator and it returns the stored energy in millijoules and joules.
Why does voltage matter so much?
Voltage is squared in the capacitor energy formula, so doubling it quadruples the stored energy. The capacitor energy calculator shows this jump clearly.
Is a charged capacitor dangerous?
A large capacitor at high voltage stores real energy and can give a serious shock. Use the capacitor energy calculator to gauge the hazard and always discharge before handling.