# Capacitor Energy Calculator

URL: https://speedycalculator.com/calculators/physics/capacitor-energy/
Last updated: 2026-10-25

> The capacitor energy calculator finds the energy stored in a capacitor, E = ½CV², and the charge it holds, Q = CV.

## Inputs

- Capacitance (µF, nF, pF, mF, F)
- Voltage (V, mV, kV)

## Results

- Stored energy
- Charge

## Formula

```
E = ½ C V²
Q = C V
```

## Explanation

Capacitors store energy in an electric field and can release it very quickly, as in camera flashes and defibrillators.

### How to use the Capacitor Energy Calculator

- **Capacitance**
- **Voltage**
- Want to work backwards? Type a value into **Stored energy** and **Voltage** is calculated for you.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Multiply half the capacitance by the square of the voltage.

### Inputs explained

FieldWhat to enterCapacitanceUnits: µF, nF, pF, mF, FVoltageUnits: V, mV, kV

### What each result means

- **Stored energy** = 0.5 × [Capacitance] × [Voltage]^2
- **Charge** = [Capacitance] × [Voltage]

### Example values

How the main result changes when **Voltage** changes and everything else stays at the example values above:

Voltage (V)Stored energy (J)12.50.367218.750.8262251.4731.252.2937.53.3505.88

## Worked example

Inputs — Capacitance: 4,700 µF; Voltage: 25 V.

Results — **Stored energy = 1.47 J**; Charge = 0.1175 C.

## FAQ

**Why does voltage matter so much?**
Energy rises with the square of voltage.

**Is it safe to touch large capacitors?**
No, they can hold a dangerous charge after power is removed.

**What formula does the Capacitor Energy Calculator use?**
E = ½ C V².

**Can I work backwards from the result?**
Yes. Type the result you want into Stored energy and the calculator finds the matching voltage.