Energy Converter
Convert between joules, calories, kWh, BTU, and other energy units instantly.
Common Conversions
| From | To |
|---|
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
Can't find what you need?
Request a ToolHow to Use the Energy Converter
This converter handles nine common energy units used in physics, nutrition, engineering, and electricity billing. All conversions pass through joules as the base unit, so every result is precise.
- Enter a value in the input field. Any positive number works, including decimals.
- Select the source unit from the "From" dropdown. For food energy, choose kilocalories (kcal), which are the "Calories" listed on nutrition labels.
- Select the target unit from the "To" dropdown. Results update instantly as you change either dropdown or the value.
- Use the swap button between the dropdowns to reverse the conversion direction with one click.
- Copy or share the result using the buttons on the result card. The share link preserves your inputs so recipients see the same conversion.
The reference table below the result shows conversions for common round values, making it easy to build intuition for the relationship between the two selected units.
About Energy Units
Energy measures the capacity to do work or transfer heat. The SI unit is the joule (J), defined as the work done by a force of one newton over one meter. In everyday life, different fields use different units for convenience. Nutritionists use kilocalories (food Calories). Electricians and utility companies use kilowatt-hours for billing. HVAC engineers use BTU (British Thermal Units) to rate heating and cooling equipment. Physicists working at atomic scales use electron volts.
One kilocalorie equals 4,184 joules. One kilowatt-hour equals 3,600,000 joules, or roughly 860 kilocalories. One BTU equals about 1,055 joules. These relationships are exact physical constants (except BTU, which has slight variations by definition).
Frequently Asked Questions
What is the difference between calories and kilocalories?
A calorie (cal) is a small unit equal to 4.184 joules. A kilocalorie (kcal) is 1,000 calories. When nutrition labels say "Calories" with a capital C, they mean kilocalories. A food item listed at 200 Calories contains 200 kcal, or 200,000 small calories. This converter lists both so you can convert in either direction without confusion.
How do I convert kWh to BTU?
One kilowatt-hour equals approximately 3,412 BTU. To convert, multiply kWh by 3,412. For example, 5 kWh equals about 17,060 BTU. This is useful when comparing electric heating costs to gas heating costs, since gas furnaces are rated in BTU per hour.
What is an electron volt and when is it used?
An electron volt (eV) is the energy gained by a single electron moving through a potential difference of one volt. It equals about 1.602 x 10^-19 joules. Particle physicists and semiconductor engineers use electron volts because atomic-scale energies are tiny in joules. For example, visible light photons carry 1.7 to 3.3 eV of energy.
How many joules are in a food calorie?
One food calorie (kilocalorie) equals exactly 4,184 joules, or about 4.184 kilojoules. A 2,000-calorie daily diet provides about 8,368 kilojoules of energy. This conversion is defined by the thermochemical calorie standard.