Energy Converter

Energy is the capacity to do work, fundamental in physics and engineering. The SI unit is the joule (1 J = 1 newton-meter = 1 watt-second), but practical contexts use many specialized units. This converter handles all major energy units: SI standard (joule, kilojoule, megajoule), nutrition (calorie = 4.184 J, kilocalorie = food Calorie used on labels worldwide), electrical (watt-hour, kilowatt-hour = 3.6 MJ used universally for residential electricity billing), American thermal (BTU = ~1,055 J used in HVAC, therm = 100,000 BTU used for natural gas), atomic physics (electronvolt for atomic energies), and mechanical (foot-pound for ballistics, erg for older astrophysics). Note the food/chemistry calorie distinction: '200 Calories' on a US food label means 200 kilocalories or 836,800 small calories. Use energy conversion for nutrition, electricity bills, fuel content, industrial heating, scientific research, and engineering thermodynamics.

The joule is the base SI energy unit, used in physics, mechanical engineering, and nutritional labeling worldwide.

The kilojoule is the standard unit on European nutrition labels and in mid-scale chemical and physical calculations.

The megajoule is used for measuring fuel energy content, large-scale electrical work, and industrial heat applications.

The kilowatt-hour is the universal billing unit for residential electricity consumption around the world.

The watt-hour is the standard unit for small-battery capacity, household electricity, and renewable-energy storage.

The calorie is the chemistry energy unit, equal to 4.184 joules and used in thermochemistry calculations.

The kilocalorie (called Calorie on US food labels) measures dietary energy in nutrition worldwide.

The British thermal unit is the standard for American HVAC systems, gas appliances, and air-conditioner ratings.

The electronvolt is the standard energy unit in atomic physics, particle physics, and semiconductor band-gap analysis.

The therm equals 100,000 BTU and is the standard unit for natural gas billing in the US and the UK.

• ✓1 kWh (kilowatt-hour) is the most common unit on electricity bills. UK household average: 2900 kWh/year.
• ✓Nutrition labels in Europe show both kJ and kcal (1 kcal = 4.184 kJ). An adult daily intake is about 2000 kcal = 8400 kJ.
• ✓BTU (British Thermal Unit) is used for HVAC and boiler ratings, mainly in the US.
• ✓The electronvolt (eV) is the energy unit of particle physics — 1 eV = 1.602 × 10⁻¹⁹ J.

• ✗Confusing calorie (scientific) with Calorie or kcal (nutrition). Food "calories" are actually kilocalories.
• ✗Mixing kWh (energy) with kW (power) on electricity specs.
• ✗Using BTU without specifying Btu/h (power) vs BTU (energy).
• ✗Treating joule and watt as interchangeable — joule is energy, watt is power (J/s).