engineering

BTU (British Thermal Unit)

A unit of heat energy equal to the amount needed to raise one pound of water by one degree Fahrenheit.

A British Thermal Unit (BTU) measures heat energy. One BTU equals the energy needed to raise the temperature of one pound of water by 1°F.

Common Uses

  • HVAC: AC units rated by BTU/hour (e.g., 12,000 BTU = 1 ton of cooling)
  • Heating: Furnace output measured in BTUs
  • Energy content: Natural gas ≈ 1,030 BTU per cubic foot

Rough Sizing Guide (AC)

  • 150–250 sq ft: 6,000 BTU
  • 250–350 sq ft: 8,000 BTU
  • 350–550 sq ft: 12,000 BTU
  • 550–700 sq ft: 14,000 BTU

Conversions

1 BTU = 1,055 joules. 1 kWh = 3,412 BTU. 1 therm = 100,000 BTU.

Related Calculators

📊 BTU Calculator📊 Energy Calculator

Related Terms

Ohm's Law

The relationship between voltage, current, and resistance in an electrical circuit: V = I × R.

Kilowatt-Hour (kWh)

A unit of energy equal to using 1,000 watts of power for one hour.

Torque

A rotational force that causes an object to rotate around an axis, measured in newton-meters or foot-pounds.

Thermal Conductivity

A material property that measures how well it conducts heat, expressed in watts per meter-kelvin (W/m·K).

Specific Heat Capacity

The amount of heat energy required to raise the temperature of one unit mass of a substance by one degree.

Stress and Strain

Stress is the internal force per unit area in a material; strain is the resulting deformation (change in shape or size).