Multiple Energy Units
Convert between joules, calories, BTU, kilowatt-hours, and more.
Nutrition & Physics
Perfect for food calories, electricity bills, and thermodynamics calculations.
Scientific Accuracy
Precise conversions for engineering, nutrition, and energy management.
Understanding Energy Conversion
Energy is the capacity to do work, measured in various units depending on the field. The SI unit is the Joule (J), used in physics and engineering. In nutrition, the Calorie (cal) or Kilocalorie (kcal) is standard. For electricity, Kilowatt-hours (kWh) are used to measure consumption over time.
One food Calorie (capital C) is actually a kilocalorie (1,000 cal), equivalent to 4,184 Joules. In heating and cooling systems, the British Thermal Unit (BTU) is common, where 1 BTU equals about 1,055 Joules. Understanding these conversions helps in everything from diet planning to calculating energy efficiency and costs.
Common Usage Examples
- Nutrition: Converting food energy from Joules to Calories
- Electricity: Calculating energy usage in kWh for billing
- HVAC: Sizing air conditioners and heaters in BTUs
- Physics: Work and energy calculations in Joules
- Exercise: Estimating energy burned during workouts
- Engineering: Mechanical work in foot-pounds
Frequently Asked Questions
What is the difference between a Calorie and a calorie?
A "small" calorie (cal) is the energy to heat 1g of water by 1°C. A "food" Calorie (kcal) is 1,000 small calories. Nutrition labels use kcal but often just call them "Calories".
How many Joules are in a kWh?
One kilowatt-hour (kWh) equals 3.6 million Joules (3.6 MJ). This is because 1 Watt = 1 Joule/second, and there are 3,600 seconds in an hour.
What is a BTU used for?
British Thermal Units (BTU) represent the heat required to raise 1 lb of water by 1°F. They are commonly used to rate the cooling or heating capacity of air conditioners and furnaces.
How do I convert Joules to Calories?
Divide Joules by 4.184 to get small calories, or by 4,184 to get food Calories (kcal). Example: 8,368 Joules ÷ 4,184 ≈ 2 kcal.