Energy Unit Converter
Convert between joules, calories, watt-hours, kilowatt-hours, BTU, electronvolts, and more energy units instantly.
About Energy Unit Converter
Our Energy Unit Converter is a comprehensive tool designed to convert energy measurements between different units quickly and accurately. Whether you're working on physics problems, engineering calculations, nutrition tracking, or energy consumption analysis, this tool provides precise conversions across ten commonly used energy units.
The tool supports conversions between Joules (J), Kilojoules (kJ), Calories (cal), Kilocalories (kcal), Watt-hours (Wh), Kilowatt-hours (kWh), Electronvolts (eV), British Thermal Units (BTU), Foot-pounds (ft·lb), and Thermies (th). All conversions are calculated with high precision and displayed instantly as you type or change units.
Convert From
How to Use
Enter the Energy Value
Type the numerical value of the energy you want to convert in the "Energy Value" field. You can enter whole numbers, decimals, or negative values. The input accepts any valid number.
Select the Original Unit
Choose the unit of your input value from the "From Unit" dropdown. Options include Joules (J), Kilojoules (kJ), Calories (cal), Kilocalories (kcal), Watt-hours (Wh), Kilowatt-hours (kWh), Electronvolts (eV), British Thermal Units (BTU), Foot-pounds (ft·lb), and Thermies (th).
Select the Target Unit
Choose the unit you want to convert to from the "To Unit" dropdown. You can also use the "Swap Units" button to quickly switch between the source and target units.
View Results
Click "Convert" to see the result. The tool will display the converted value, the formula used, and all possible conversions from your original value to every supported unit.
Common Conversions
Quick links to frequently used energy conversions. Click any link to see the instant result.
Frequently Asked Questions
What is the SI unit for energy?
The SI unit for energy is the Joule (J). It is defined as the work done when a force of one newton moves an object one meter. One joule is also equivalent to one watt-second (1 W·s) or one kilogram meter squared per second squared (1 kg·m²/s²).
What is the difference between calories and kilocalories?
In nutrition, what is commonly called a "Calorie" (with a capital C) is actually a kilocalorie (kcal). 1 kilocalorie = 1000 calories. The small calorie (cal) is the amount of energy needed to raise 1 gram of water by 1°C, while the kilocalorie raises 1 kilogram of water by 1°C.
How precise are the conversions?
Our converter uses high-precision mathematical calculations and displays results with up to 10 decimal places. For most practical applications, 2-4 decimal places are sufficient. You can round the result as needed for your specific use case.
What is a British Thermal Unit (BTU)?
A British Thermal Unit (BTU) is a traditional unit of energy commonly used in the power, steam generation, and heating and air conditioning industries. One BTU is approximately the energy needed to heat one pound of water by 1°F. 1 BTU ≈ 1055.06 joules.
What is an electronvolt?
An electronvolt (eV) is a very small unit of energy used in atomic and particle physics. It represents the energy gained by a single electron moving across an electric potential difference of one volt. 1 eV ≈ 1.602 × 10⁻¹⁹ joules.
Is this tool free to use?
Absolutely! Our Energy Unit Converter is completely free to use, with no registration required. We believe in providing high-quality, accessible tools for students, engineers, scientists, and anyone who needs to perform energy conversions quickly and accurately.