Calculation results
| Charge | ||
| Energy |
Created by CalculatorOK Team · Last updated: Jul 6, 2025
Capacitor Energy & Charge Calculator ⚡
What this capacitor calculator computes
Every charged capacitor stores a small reservoir of energy that persists even after power is removed. This tool takes Capacitance and Voltage and returns both stored energy and electric charge, in whichever Charge unit and Energy unit you select. Electronics hobbyists sizing camera flashes, engineers smoothing power supplies, and physics students checking homework all end up here.
The two outputs answer different questions. Energy describes heating and flash capability, while charge counts how many electrons moved onto the plates.
Two little formulas doing the work
Stored energy follows E = 0.5 C V^2 and stored charge follows Q = C V, with capacitance in farads and voltage in volts. Both results grow linearly with capacitance, but only the energy is quadratic in voltage.
Work an example with a 1000 microfarad capacitor charged to 12 volts, which is 0.001 farads. Stored energy is E = 0.5 x 0.001 x 144, which equals 0.072 joules. Charge is Q = 0.001 x 12 = 0.012 coulombs, or 12 millicoulombs. Doubling the voltage to 24 would have quadrupled the energy to 0.288 joules while only doubling the charge.
How to use it, step by step
Enter Capacitance in farads, remembering that 1000 microfarads is 0.001 farads and small ceramic values are even smaller fractions. Enter Voltage next, then choose your preferred Charge unit and Energy unit from their selectors. Press Calculate and both results appear together.
A handy anchor point: 1 farad at 1 volt stores 0.5 joules and 1 coulomb, while a 1 farad supercapacitor at 5 volts stores 12.5 joules. Large electrolytic capacitors can hold an uncomfortable jolt, so discharge through a resistor before touching circuitry.
Frequently Asked Questions
How much energy does a capacitor store?
Stored energy equals half the capacitance times voltage squared, written E = 0.5 C V^2. A 1000 microfarad capacitor charged to 12 volts therefore holds 0.072 joules.
How is charge related to voltage?
Charge follows Q = C V, so it scales linearly with voltage. The same 1000 microfarad capacitor at 12 volts carries 0.012 coulombs, which is 12 millicoulombs.
Why double the voltage but quadruple energy?
Energy depends on voltage squared in E = 0.5 C V^2. Raising 12 volts to 24 volts multiplies energy by four, from 0.072 to 0.288 joules, while charge merely doubles.
How do I convert microfarads to farads?
Divide the microfarad value by one million, so 1000 microfarads becomes 0.001 farads. The calculator expects farads and then reports charge and energy in whichever units you select.
Is a charged capacitor dangerous to touch?
It can be, because stored energy discharges instantly through your body or a screwdriver. Discharge large capacitors through a resistor before handling them, even after the equipment is switched off.