Simple Explanation

A unit of heat—how much energy it takes to raise the temperature of one pound of water by one degree Fahrenheit.

Concise Technical Definition

The amount of heat required to raise the temperature of one pound of water by 1°F, typically from 59°F to 60°F, at a constant pressure of one atmosphere.

Layman-Friendly Analogy

Like the heat from one wooden match—just enough to warm up a small amount of water slightly.

Industry Usage Summary

Commonly used in heating, ventilation, and air conditioning (HVAC) to quantify energy output of furnaces, air conditioners, and heaters. Also used in power generation to compare fuel efficiency.

Engineering Shortcut

1 BTU ≈ 1055 joules; 1 watt = 3.41 BTU/hr

Full Technical Explanation

The British Thermal Unit (BTU) is a non-SI unit of heat still widely used in the US. It is defined as the amount of heat required to raise the temperature of 1 pound of water by 1°F. It’s equivalent to approximately 1055.06 joules of energy.