Capacitor Energy Calculator | Online Free Tool | Elysia Tools
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Capacitor Energy Calculator
U = ½·C·V² with capacitance and voltage unit selectors, the stored charge Q = C·V, and auto-scaled energy output.
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Samples
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Tool usage guide
Learn when to use this tool, what it supports, and how real users apply it.
Key facts
Category
Science & Education
Input types
number, select
Output type
text
Sample coverage
4
API ready
Yes
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.
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
1Enter the capacitance value and choose its unit (F, mF, µF, nF, or pF).
2Enter the operating voltage across the capacitor and select the voltage unit (mV, V, or kV).
3The 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.
Examples
1. Supercapacitor Backup Energy Analysis
Embedded Systems Engineer
Background
Designing an IoT sensor node with a single-cell supercapacitor to keep the real-time clock alive during battery swaps.
Problem
Need to determine total energy and charge available in a 1 F supercapacitor charged to 2.7 V.
How to use
Input 1 into Capacitance with unit 'F', and 2.7 into Voltage with unit 'V'.
Capacitance: 1 F, Voltage: 2.7 V
Outcome
Calculates an energy output of U = 3.645 J and a stored charge of Q = 2.7 C.
2. High-Voltage Pulse Capacitor Sizing
Biomedical Equipment Designer
Background
Specifying high-energy discharge stages for medical defibrillator circuitry.
Problem
Calculate the exact energy delivered by a 200 µF capacitor charged to 2 kV.
How to use
Set Capacitance to 200 with unit 'uF' (µF) and Voltage to 2 with unit 'kV'.
FAQ
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.