How to Use This Tool
Enter a Value
Type the energy value you want to convert into the input field. Decimals and scientific notation are supported.
Choose Your Units
Pick a From unit and a To unit from the dropdowns. Use the swap button to flip them instantly.
Read the Result
The converted value appears instantly below the inputs. Click Copy to put it on your clipboard.
See All Conversions
Scroll down to see the same energy converted into every other supported unit at once.
Frequently Asked Questions
Is this tool really free?
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Yes, completely free with no limits and no sign-up. Everything runs in your browser with no server costs.
Is my data sent to a server?
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No. All conversion math happens directly in your browser. Nothing you type is ever sent anywhere.
What units are supported?
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12 units: Joule, Kilojoule, Megajoule, Calorie, Kilocalorie, Watt-hour, Kilowatt-hour, Electronvolt, BTU, Foot-pound, Erg, and Therm.
What is the difference between a Calorie and a Kilocalorie?
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A Calorie (lowercase) is a small unit of energy equal to about 4.184 joules. A Kilocalorie (kcal) is 1,000 calories and is what food labels call a 'Calorie' (uppercase C). When a food label says 200 Calories, it means 200 kilocalories.
What is a BTU?
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BTU stands for British Thermal Unit. It is the amount of energy needed to raise one pound of water by one degree Fahrenheit. BTU is commonly used to rate heating and cooling systems, water heaters, and grills.
What is a Kilowatt-hour?
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A kilowatt-hour (kWh) is the energy used by a 1,000-watt appliance running for one hour. It is the standard unit on electricity bills worldwide.
What is an Electronvolt?
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An electronvolt (eV) is a tiny unit of energy used in physics and chemistry to describe the energy of individual particles, photons, and atomic-scale processes.
What is a Therm?
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A therm equals 100,000 BTU. It is commonly used by gas companies in the US and UK to measure natural gas consumption on utility bills.
How accurate are the conversions?
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The tool uses standard conversion factors and displays up to 10 significant figures. Results are accurate for everyday, educational, and professional use.
Can I see all conversions at once?
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Yes. Below the main result, the tool shows the same value converted into every other unit in a scrollable list.
What Is Energy Converter?
Energy Converter is a free tool that converts between 12 energy units right in your browser. It covers scientific units (joule, kilojoule, megajoule, electronvolt, erg), food energy (calorie, kilocalorie), electrical energy (watt-hour, kilowatt-hour), and heating and gas units (BTU, foot-pound, therm). Nothing you type is ever sent anywhere - all math runs locally on your device.
The result updates live as you type, and a full conversion table shows the same value in every other unit at once. Use the swap button to flip your units instantly, or copy the result to your clipboard in one click.
Features Explained
12 Energy Units
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Convert between Joule, Kilojoule, Megajoule, Calorie, Kilocalorie, Watt-hour, Kilowatt-hour, Electronvolt, BTU, Foot-pound, Erg, and Therm.
Joule Family
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Joule is the standard scientific unit of energy. Kilojoule and Megajoule scale it up for food labels, engineering, and industrial use.
Calories and Kilocalories
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Calorie is a small unit used in chemistry. Kilocalorie is what food labels call a Calorie - the tool helps you tell them apart and convert between them.
Electrical Energy
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Watt-hour and Kilowatt-hour are the units on your electricity bill. Convert between kWh and joules or BTU to understand energy costs.
Heating and Gas Units
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BTU is used for heating and cooling ratings. Therm (100,000 BTU) is used on natural gas bills. Foot-pound measures mechanical work.
Physics Units
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Electronvolt for atomic-scale energy and Erg for very small measurements in physics. Convert these to everyday units for quick reference.
Instant Conversion
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The result updates live as you type. There is no Convert button to click - you see the answer the moment your input changes.
All Conversions at Once
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Below the main result, a scrollable table shows the same energy converted into every other unit simultaneously.
Swap Button and Copy
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Click the swap button to flip From and To instantly. Click Copy to put the result on your clipboard, ready to paste anywhere.
100% Browser-Based
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All conversion math runs directly in your browser. Nothing you type is ever sent to any server - complete privacy.
Who Is This Tool For?
Students
Convert between joules, calories, and electronvolts for physics, chemistry, and engineering homework.
Teachers
Demonstrate energy conversions in real time during lessons and help students understand the relationships between different units.
Engineers
Convert between joules, BTU, kWh, and foot-pounds for mechanical, electrical, and thermal system calculations.
Electricians
Convert between watt-hours, kilowatt-hours, and joules when sizing circuits, batteries, and solar panels.
HVAC Technicians
Convert between BTU, kWh, and therms when sizing heating, cooling, and ventilation systems.
Nutritionists
Convert between calories, kilocalories, and kilojoules for diet planning, food labeling, and nutrition education.
Fitness Enthusiasts
Convert exercise energy expenditure between kilocalories and kilojoules when using equipment or apps from different regions.
Homeowners
Convert between kWh and BTU to understand your electricity and gas bills and compare energy costs.
Solar Panel Owners
Convert solar output between watt-hours, kilowatt-hours, and joules to understand your system's production.
Physicists
Convert between joules, electronvolts, and ergs for research, experiments, and publications.
Chemists
Convert reaction energies between calories, joules, and kilojoules for thermodynamic calculations.
Environmental Scientists
Convert energy figures between kWh, BTU, and therms for carbon footprint and sustainability reports.
Oil and Gas Workers
Convert between BTU, therms, and joules for production data, energy content calculations, and regulatory reporting.
Utility Workers
Convert between kWh, BTU, and therms for meter readings, billing, and load calculations.
Automotive Engineers
Convert fuel energy content between joules, BTU, and kilocalories for engine efficiency and emissions calculations.
Brewers
Convert heating energy between BTU, kWh, and kilojoules when sizing burners and heat exchangers.
Bakers
Convert oven energy usage between kWh and BTU when comparing equipment or estimating operating costs.
Researchers
Convert between SI and traditional energy units for cross-referencing data across different fields and publications.
Journalists
Convert energy figures in stories about power plants, energy policy, and climate so readers in different regions understand.
Real Estate Agents
Convert energy ratings and utility costs between kWh and BTU for property listings and energy efficiency comparisons.
Architects
Convert building energy specifications between kWh, BTU, and megajoules for green building certifications.
Preppers and Off-Grid Living
Convert battery storage, fuel energy, and generator output between kWh, BTU, and joules for self-sufficiency planning.
Parents
Understand food energy labels by converting between kilocalories and kilojoules, since different countries use different units.
Anyone
Quickly convert any energy value for any reason - bills, homework, nutrition, curiosity, or work.
Tips for Best Results
Calorie vs Kilocalorie
Food labels use 'Calorie' (capital C) to mean kilocalorie. So 200 food Calories = 200 kcal = 200,000 small calories. This tool uses the precise terms.
kWh for electricity
Your electricity bill is measured in kilowatt-hours. 1 kWh = 3,600,000 joules = about 3,412 BTU. Use this conversion to compare electric and gas costs.
BTU for heating and cooling
Air conditioners, furnaces, and water heaters are rated in BTU per hour. A therm is 100,000 BTU, used on gas bills.
Electronvolt is tiny
1 eV = about 1.602 x 10 to the minus 19 joules. It is used for atomic and particle physics, not everyday energy. Type scientific notation like 1.6e-19.
Use the All Conversions table
Scroll below the main result to see the same energy in every other unit at once. Great for comparing across scientific and practical scales.
Use the swap button
Click the swap button between the dropdowns to flip From and To instantly instead of changing both dropdowns manually.
Copy the result in one click
Click Copy next to the result to put the value on your clipboard, ready to paste into a report, spreadsheet, or message.
Erg is very small
1 erg = 0.0000001 joules. It is an older unit still used in some physics and astronomy contexts.
Foot-pound for mechanical work
A foot-pound is the energy to lift one pound by one foot. It is used in mechanics, ballistics, and torque specifications.
Privacy is built in
Nothing you type is ever sent to any server. All math runs in your browser, so your data stays completely private.
Privacy & Security
This tool runs 100% in your browser. Your files stay entirely on your own device. Nothing is uploaded, nothing is shared, and no server, advertiser, or third party has access to your files.
If a tool saves your work on your own device, you can remove it at any time using the Clear All button. Some tools rely on an external service to return their result; in those cases, only the minimum data required for the request is sent, and never your files or content. Any ads shown on this page run in an isolated frame and cannot read, touch, or transmit anything you upload, paste, type, or download here. Advertisers may see standard visit information like your IP address and which page you're on, as described in our Privacy Policy, but your data itself stays fully under your control.
