Calculate the energy stored in a capacitor from its capacitance and voltage, or the voltage or capacitance from the energy. The stored charge is shown too.
Last updated: November 8, 2026
E = ½ × C × V²
A capacitor stores energy in the electric field between two conductors: • E = ½ × C × V² • Q = C × V • V = √(2E ÷ C), C = 2E ÷ V² • C in farads: 1 µF = 10⁻⁶ F Example: a 1,000 µF capacitor charged to 12 V stores ½ × 0.001 × 12² = 0.072 J and a charge of 0.001 × 12 = 0.012 C = 12 mC. Because energy grows with the square of voltage, doubling the voltage quadruples the energy. High-voltage capacitors can be dangerous even when switched off; discharge them before touching.
Common questions about capacitor energy
E = ½ × C × V². With capacitance in farads and voltage in volts, the energy is in joules.
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In microfarads (µF).
In volts.