# Capacitor Energy Calculator

> Calculate the energy stored in a capacitor and its charge from capacitance in F, mF, µF, nF or pF and the voltage across it, using E = ½CV² and Q = CV.

Category: Science & engineering · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/capacitor-energy-calculator

A charged capacitor stores energy E = ½CV². Because energy rises with the square of voltage, doubling the voltage stores four times as much.

Also called: Capacitor charge calculator, Stored energy calculator.

## Inputs
- Capacitance (default 1000)
- Capacitance unit (options: farads (F), millifarads (mF), microfarads (µF), nanofarads (nF), picofarads (pF); default uf)
- Voltage across the capacitor (unit V; default 50)

## Results
- Stored energy
- Stored energy
- Stored energy
- Charge
- Charge

## Formula

```
E = ½ × C × V²;  Q = C × V;  Wh = J ÷ 3600
```

Where:
- C: capacitance in farads
- V: voltage in volts
- E: energy in joules
- Q: charge in coulombs

## Worked example
1. C = 1000 µF = 0.001 F.
2. E = ½ × 0.001 × 50² = 1.25 J.
3. Q = 0.001 × 50 = 0.05 C = 50 mC.

**Result:** A 1000 µF capacitor charged to 50 V stores 1.25 J and holds 50 mC of charge.

## What the result means

Only part of this energy is usable if the load stops working below some minimum voltage: usable energy = ½C(V₁² − V₂²).

## Assumptions and limits
- Ideal capacitor with constant capacitance.
- Leakage, ESR losses and capacitance tolerance (often ±20%) are not included.

## Questions

### Is a charged capacitor dangerous?

Large capacitors at high voltage can deliver a dangerous shock long after power is removed. Discharge them through a suitable resistor before handling.

### Why only half of CV²?

The voltage rises from 0 to V as charge is added, so the average voltage during charging is V ÷ 2.

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/capacitor-energy-calculator