Energy Conversion Matrix

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.

• ✓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).