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Sumivo · Electrical

Capacitor Charge Calculator

Calculate electric charge and stored energy from capacitance and voltage.

01 / INPUTS

F
V

02 / RESULT

ELECTRIC CHARGE

0.01 C

Charge
0.01 C
Stored energy
0.05 J

Calculation trace

  1. 0.001 F × 10 V = 0.01 C
    0.01 C
    Charge
  2. 0.5 × 0.001 F × 10² V = 0.05 J
    0.05 J
    Stored energy
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How it works

For capacitance C in farads and voltage V in volts, the tool computes the stored charge as Q = C·V in coulombs and the stored energy as E = ½C·V² in joules. Charge grows linearly with both C and V, while energy grows with the square of the voltage — so doubling the voltage doubles the charge but quadruples the energy. For example, a 1000 µF capacitor (0.001 F) held at 10 V stores Q = 0.001 × 10 = 0.01 C and E = ½ × 0.001 × 10² = 0.05 J. This is the steady-state charge on a fully charged capacitor; it is a different quantity from how long a capacitor takes to charge through a resistor, which follows the RC time constant τ = R·C and is not what this calculator computes.

Assumptions & limits

  • Models an ideal capacitor at the entered steady voltage; it does not model leakage, equivalent series resistance or charging time.
  • Q = C·V is the total charge stored at the entered voltage, not a charging-time or transient result.
  • Capacitance and voltage must both be positive finite numbers, entered in base units (farads and volts).
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FAQ

What does one coulomb represent for a capacitor?
A capacitor holds one coulomb when a capacitance of one farad has one volt across it, because Q = C·V.
Is capacitor charge the same as capacitor charging time?
No. Charge Q = C·V (in coulombs) is how much charge is stored at a given voltage. Charging time is a separate problem: a capacitor charges through a resistance R with time constant τ = R·C, reaching about 63% of the supply voltage after one τ and effectively full after about five. This calculator computes the stored charge and energy, not the charging time.
How do I get the energy stored, not just the charge?
The tool shows both. Stored energy is E = ½C·V² in joules alongside the charge Q = C·V. For the 0.001 F, 10 V example that is 0.05 J.
What units should I use for capacitance?
Farads (F). Real capacitors are usually marked in microfarads (µF), nanofarads (nF) or picofarads (pF), so convert first: 1000 µF = 0.001 F, and 1 nF = 0.000000001 F. Entering microfarads as if they were farads is the most common mistake here.
Does higher voltage or higher capacitance store more charge?
Both raise the charge by the same proportion, because Q = C·V is linear in each. Energy behaves differently: it rises with the square of the voltage (E = ½C·V²), so raising the voltage adds far more energy than raising the capacitance by the same factor.
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