Unit Converters
Energy Converter
Convert energy units: joules, calories, kilocalories, BTU, kilowatt-hours, electronvolts, and more. Perfect for physics, nutrition, engineering, and scientific calculations.
Use Energy Converter to get instant results without uploads or sign-ups. Everything runs securely in your browser for fast, reliable output.
Your results will appear here.
About this tool
Energy conversion is fundamental in physics, engineering, nutrition, and everyday applications. Different fields use different energy units: physics often uses joules and electronvolts, nutrition uses calories and kilocalories, HVAC uses BTU, and utilities measure electrical energy in kilowatt-hours. Understanding these conversions is essential for comparing energy consumption, calculating efficiency, and solving scientific problems.
Our Energy Converter handles all common energy units with precision. Convert between SI units (joules, kilojoules), nutritional units (calories, kilocalories/Calories), thermal units (BTU, therms), electrical units (watt-hours, kilowatt-hours), and atomic-scale units (electronvolts). The calculator uses exact conversion factors based on international standards.
Energy conversions are crucial in many contexts: comparing fuel efficiency of vehicles, understanding food energy content, calculating heating costs, analyzing battery capacity, converting between mechanical and thermal energy, and working with particle physics data. For example, food labels often show energy in both kilocalories (Calories) and kilojoules.
The converter is valuable for students studying thermodynamics or physics, engineers designing energy systems, nutritionists calculating dietary energy, homeowners comparing heating options, and anyone trying to understand energy consumption. Accurate energy conversions help make informed decisions about energy efficiency, cost, and environmental impact.
Usage examples
Food Energy
Convert 2,000 kilocalories (Calories) to kilojoules
2,000 kcal = 8,368 kJ
Electrical Usage
Convert 5 kWh of electricity to megajoules
5 kWh = 18 MJ
Heating Energy
Convert 10,000 BTU to kilojoules
10,000 BTU = 10,551 kJ
Physics Problem
Convert 1 MeV (million electronvolts) to joules
1 MeV = 1.602 × 10⁻¹³ J
Small Energy
Convert 100 calories to joules
100 cal = 418.4 J
How to use
- Enter the energy value you want to convert.
- Select the unit you're converting FROM (e.g., joules).
- Select the unit you're converting TO (e.g., calories).
- Click "Convert" to see the result instantly.
- The converter shows precise results with scientific notation for very large or small values.
- Useful for physics problems, nutrition calculations, and energy efficiency analysis.
Benefits
- Convert between all common energy units instantly
- Accurate conversions using internationally recognized standards
- Essential for physics and engineering calculations
- Useful for nutrition and dietary energy analysis
- Helps compare energy efficiency across different systems
- Perfect for students learning thermodynamics
- Simplifies HVAC and heating system comparisons
- Handles both macroscopic and atomic-scale energy units
- Free alternative to manual conversion calculations
- Prevents errors in scientific and engineering work
- Mobile-friendly for quick reference
- Supports scientific notation for very large or small values
FAQs
What is the difference between calories and Calories?
A small calorie (cal) is the energy to heat 1 gram of water by 1°C. A large Calorie (Cal or kcal) used in nutrition equals 1,000 small calories. Food labels showing "Calories" actually mean kilocalories. So a 200 Calorie snack contains 200,000 calories or about 837 kilojoules.
How many joules are in a kilowatt-hour?
One kilowatt-hour (kWh) equals 3,600,000 joules or 3.6 megajoules. This is because 1 kWh = 1,000 watts × 3,600 seconds = 3,600,000 watt-seconds (joules). Your electric bill typically measures usage in kWh, which represents sustained energy consumption.
What is a BTU and when is it used?
BTU (British Thermal Unit) is the energy to raise 1 pound of water by 1°F. It's commonly used in HVAC, with air conditioners and heaters rated in BTU/hour. One BTU equals approximately 1,055 joules or 252 calories. A 10,000 BTU air conditioner removes 10,000 BTU of heat per hour.
How do I convert food energy between different units?
Food labels may show kilocalories (kcal/Cal) or kilojoules (kJ). To convert: multiply kcal by 4.184 to get kJ, or divide kJ by 4.184 to get kcal. A 2,000 Calorie diet equals about 8,368 kJ. Many countries require both units on food labels.
What is an electronvolt (eV)?
An electronvolt is the energy gained by an electron moving through a 1-volt potential. It's incredibly small: 1 eV = 1.602 × 10⁻¹⁹ joules. Used in atomic and particle physics, with keV (thousand), MeV (million), and GeV (billion) for larger energies. X-rays are measured in keV.
Why are there so many different energy units?
Different fields evolved their own convenient units. Joules are SI standard for physics. Calories emerged from chemistry. BTU from American engineering. kWh for billing electricity. eV for atomic physics. Each is most convenient in its domain, but conversions are needed for cross-disciplinary work.
How much energy does a typical home use?
A US home averages about 900 kWh per month (about 30 kWh/day or 3.24 gigajoules/day). This varies by climate, size, and efficiency. In other units: 900 kWh = 3,240 MJ = 3.07 million BTU = 773,000 kilocalories. Heating and cooling are typically the largest consumers.
Can I use this to compare fuel types?
Yes! Different fuels have characteristic energy content per unit. Gasoline contains about 34 MJ/liter (120 MJ/gallon). Natural gas has about 37 MJ/cubic meter. Coal has about 24 MJ/kg. Comparing energy content helps evaluate fuel costs and efficiency across different energy sources.
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