A capacitor stores electrical charge when connected to a voltage source — the Capacitor Charge Calculator tells you exactly how much. Enter your capacitance (in F, mF, µF, nF, or pF) and voltage to get the Charge (Q) in coulombs and Energy Stored (E) in joules. Optionally add a series resistance to also calculate the Time Constant (τ) — how quickly the capacitor charges or discharges.
Charge (Q)
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Energy Stored (E)
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Time Constant (τ)
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The energy stored in a capacitor is the electrical potential energy accumulated between its plates due to the electric field created by separated charges. This energy can be calculated using the formula E = ½CV².
A capacitor stores energy by accumulating electric charges on its plates. When voltage is applied, electrons accumulate on one plate while the other becomes positively charged, creating an electric field that stores potential energy.
Use the formula E = ½CV², where E is energy in joules, C is capacitance in farads, and V is voltage in volts. You can also use E = ½QV where Q is the charge in coulombs.
The charge stored by a capacitor is calculated using Q = CV, where Q is charge in coulombs, C is capacitance in farads, and V is voltage in volts. This represents the total amount of electric charge accumulated on the capacitor plates.
The time constant (τ) equals RC, where R is series resistance and C is capacitance. It represents the time needed for the capacitor to charge to about 63% of the supply voltage or discharge to 37% of its initial voltage.
The factor of ½ in the energy formula E = ½CV² comes from the integration of power over time during charging. As the capacitor charges, voltage increases linearly while current decreases, resulting in the average power being half the maximum.
Common capacitance units include farads (F), millifarads (mF), microfarads (µF), nanofarads (nF), and picofarads (pF). Most practical capacitors are measured in µF, nF, or pF, with 1F = 1,000,000µF = 1,000,000,000nF.