Energy Converter
This energy converter lets you convert between eight common energy units in one step: joules (J), kilojoules (kJ), megajoules (MJ), small calories (cal), kilocalories (kcal), kilowatt-hours (kWh), British Thermal Units (BTU), and electronvolts (eV). Energy is the same physical quantity no matter which unit you use, but the numbers vary enormously: one kilowatt-hour is 3,600,000 joules but only 3.6 megajoules, and the same amount of energy is also 860.42 kilocalories or 3,412 BTU. The joule is the SI base unit and serves as this converter's internal reference point: you pick a unit, enter a value, and the converter multiplies it by a fixed factor to get joules, then divides by each output factor to show all seven remaining units at once. Kilojoules and kilocalories are widely used in nutrition, where food energy is labelled in kJ or kcal (the Calorie written with a capital C is always a kilocalorie). Kilowatt-hours are the standard billing unit for electricity. BTU are used in the United States for heating and cooling equipment. Electronvolts are used in physics and chemistry for atomic-scale energies. You provide one value in any unit and you receive all the equivalents instantly. The tool suits students, engineers, nutritionists, energy auditors, and anyone comparing energy values across different standards or industries. The conversion factors are exact constants based on international definitions.
How it works
Each energy unit has a fixed conversion factor to joules. The converter multiplies your input by the appropriate factor to get joules, then divides by each output factor to produce all results at once. The factors used are: 1 kJ = 1,000 J; 1 MJ = 1,000,000 J; 1 cal = 4.184 J; 1 kcal = 4,184 J; 1 kWh = 3,600,000 J; 1 BTU = 1,055.06 J; 1 eV = 1.602176634 x 10^-19 J (exact, 2019 SI definition). All other conversions are derived from these fixed values.
Worked example
Starting from 1 kWh: 1 times 3,600,000 gives 3,600,000 J, which is 3,600 kJ and 3.6 MJ. Dividing by 4,184 gives 860.42 kcal. Dividing by 1,055.06 gives 3,412.14 BTU. These match the default values pre-filled in the converter above, so you can verify each output without changing anything.
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