Convert between Joules, kilojoules, calories, kilocalories, Wh, kWh, BTU, and eV
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Convert between metric and imperial units for length, weight, temperature, and more
Convert between Pascal, kPa, bar, atm, PSI, mmHg, and inHg
Convert between Celsius, Fahrenheit, Kelvin, and Rankine temperature scales
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Energy Converter is a free online tool that converts energy measurements between eight units: Joules, kilojoules, calories, kilocalories (food Calories), watt-hours, kilowatt-hours, BTU, and electronvolts. This tool is essential for physics, engineering, nutrition, electricity billing, HVAC calculations, and any field that deals with energy in different forms. Energy is the capacity to do work, and different fields measure it in different units for historical and practical reasons. The Joule is the SI unit of energy. Kilocalories (often just called Calories with a capital C on food labels) measure the energy content of food. Kilowatt-hours are the standard billing unit for electricity. BTU (British Thermal Units) are used in HVAC, heating, and air conditioning. Electronvolts are used in atomic and particle physics for extremely small energy values. The relationship between these units reflects fundamental physics: 1 calorie is exactly 4.184 joules, 1 kWh is exactly 3,600,000 joules, and 1 BTU is approximately 1,055 joules. Enter any energy value and select the source unit to see all conversions instantly. All calculations run entirely in your browser.
Key conversion factors: 1 kJ = 1,000 J = 0.2388 kcal = 0.2778 Wh 1 kcal = 4,184 J = 4.184 kJ = 3.968 BTU 1 kWh = 3,600,000 J = 3,600 kJ = 860.4 kcal 1 BTU = 1,055.06 J = 0.2520 kcal 1 eV = 1.602 x 10^-19 J Examples: A 2000 kcal daily diet = 8,368 kJ = 2.33 kWh 1 kWh of electricity = 860 kcal = 3,412 BTU