Energy Converter

A calorie (cal) is the energy needed to raise 1 gram of water by 1 degree C, equal to 4.184 J. A kilocalorie (kcal) is exactly 1,000 of those calories, or 4,184 J. Food labels in the US use "Calories" (capital C) to mean kcal, so a 250-Calorie snack contains 250 kcal, not 250 small calories.

US food labels report energy in kcal but write it as "Calories" (capital C). Most fitness apps adopt the same shorthand and display kcal as "calories." The numbers are identical: 1 food Calorie = 1 kcal = 1,000 small cal = 4,184 J. No conversion is needed between what you eat and what your app burns.

A kilowatt-hour (kWh) is the energy a 1,000-watt device consumes in one hour, equal to 3,600,000 J (3.6 MJ). If your bill shows 500 kWh for the month, that is 1.8 billion joules, or roughly 430,000 kcal.

The British Thermal Unit is the traditional US measure of heating and cooling capacity. One BTU equals 1,055.06 J. AC units are rated in BTU/h: a 12,000 BTU/h window unit removes about 3,517 watts of heat, enough to cool a 450 to 550 sq ft room depending on insulation and climate.

An electronvolt (eV) is the energy one electron gains when it moves through a 1-volt potential difference, equal to 1.602176634 x 10^-19 J. The unit is used in atomic and particle physics because everyday joules produce unwieldy small numbers at that scale. Visible-light photons carry roughly 1.8 to 3.1 eV depending on color.