# Capacitor Energy Calculator

U = ½·C·V² with capacitance and voltage unit selectors, the stored charge Q = C·V, and auto-scaled energy output.

> Canonical page: https://elysiatools.com/en/tools/energy-stored-capacitor

- **Category:** Science & Education

- **Keywords:** capacitor energy, stored energy, capacitance voltage, joules, charge storage, electromagnetism

## Overview

The Capacitor Energy Calculator computes the electrical potential energy stored in an electrostatic field using the formula U = ½·C·V² and evaluates the total stored charge via Q = C·V. With flexible unit pickers for both capacitance and voltage, it provides instant, auto-scaled outputs in joules and coulombs without manual unit conversions.

## Inputs

- **Capacitance C** (number): e.g. 1
- **Capacitance unit** (select)
- **Voltage V** (number): e.g. 2.7
- **Voltage unit** (select)

## When to use

- Sizing pulse-power storage capacitors or backup supercapacitor banks for electronic devices.
- Analyzing safety discharge requirements and stored energy levels in high-voltage circuit designs.
- Solving physics and electrical engineering problems involving capacitance, voltage, charge, and energy.

## How it works

- Enter the capacitance value and choose its unit (F, mF, µF, nF, or pF).
- Enter the operating voltage across the capacitor and select the voltage unit (mV, V, or kV).
- The tool normalizes inputs to base SI units (farads and volts), evaluates stored energy U = ½·C·V² and charge Q = C·V, and presents the formatted results.

## Use cases

- Hardware engineers calculating energy storage in decoupling capacitors and backup power rails.
- Power electronics designers sizing high-voltage pulse capacitors for discharge systems and defibrillator circuits.
- STEM educators and students verifying electromagnetism homework calculations and laboratory measurements.

## Frequently asked questions

### What is the formula used to calculate stored energy in a capacitor?

Stored energy is calculated as U = ½·C·V², where C is capacitance in farads, V is potential difference in volts, and U is energy in joules.

### How is stored electrical charge calculated?

Stored charge is computed using the relationship Q = C·V, yielding the total charge Q in coulombs.

### Why does doubling the voltage quadruple the stored energy?

Energy scales quadratically with voltage (V²), meaning any multiplier applied to voltage increases energy by that multiplier squared.

### Which capacitance and voltage units are supported?

Capacitance supports F, mF, µF, nF, and pF. Voltage supports millivolts (mV), volts (V), and kilovolts (kV).

### Can I use this calculator for supercapacitors?

Yes, enter the rated capacitance in farads (F) and the cell working voltage in volts (V) to determine the energy and charge capacity.

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