Capacitor Energy Calculator

How it is calculated

A charged capacitor stores energy E = ½·C·V² and charge Q = C·V. Enter the capacitance C in microfarads (µF) and the voltage V in volts. The tool converts C to farads (× 10⁻⁶), then reports energy in millijoules and charge in microcoulombs. Because voltage is squared, doubling V quadruples the energy but only doubles the charge. Capacitance cannot be negative. The result is the ideal stored energy: it ignores leakage, the series resistance of the part, and the fact that you can never discharge a capacitor to exactly zero volts in a real circuit.

Common mistakes

• Entering capacitance in farads or nanofarads. The field expects microfarads.
• Forgetting the square: the energy depends on V², not on V.
• Using the capacitor's voltage rating instead of the voltage it is actually charged to.
• Reading millijoules as joules or confusing mJ with µC. They are different quantities.