Calorie to BTU Converter

A calorie (cal), also called a small calorie or gram calorie, is a unit of energy equal to approximately 4.184 joules. It represents the energy needed to raise the temperature of one gram of water by one degree Celsius at standard atmospheric pressure.

The calorie was defined by French chemist Nicolas Clément in 1824 as a unit for measuring heat. It was widely used in chemistry and physics for calorimetry and thermodynamics before being largely replaced by the joule in scientific applications, though it remains in use for food energy.

Calories are primarily used in chemistry for small-scale energy measurements, in some scientific literature, and occasionally in food and nutrition contexts. However, they've been largely replaced by joules in scientific applications and by kilocalories (food calories) in nutrition.

A British Thermal Unit (BTU) is a unit of energy equal to approximately 1,055 joules. It represents the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit at standard atmospheric pressure.

The BTU was developed in the 19th century as part of the British Imperial system for measuring heat energy. It became standard in heating, ventilation, and air conditioning (HVAC) applications in countries using imperial units, particularly for rating heating and cooling equipment capacity.

BTUs are extensively used in the United States for HVAC system ratings, heating and cooling equipment specifications, and energy content of fuels. They're standard for furnace output ratings, air conditioner capacity, water heater specifications, and natural gas energy content measurements.