British Thermal Unit

Team Physics -
Created by: Team Physics -, Last Updated: April 25, 2024

British Thermal Unit

What is a British Thermal Unit?

The British Thermal Unit (BTU) is a unit of energy commonly used in the United States and UK to measure heating and cooling energy. It represents the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit.

Q = M x Cp x ΔT

The formula to calculate British thermal units (BTUs) is:

BTU=mass×specific heat×Δtemperature


  • Mass is the mass of the substance being heated or cooled.
  • Specific heat is the specific heat capacity of the substance.
  • ΔTemperature is the change in temperature

British Thermal Unit Formula

The Basic Formula for Work and Energy

The basic formula for work and energy involving British thermal units (BTUs) is:

W = F×D


  • W can represent the energy required to heat or cool a substance.
  • F could represent the amount of energy applied to transfer heat to or from a substance, measured in pounds of force.
  • D represents the distance over which the heat energy is transferred, such as the length of a heating or cooling coil or the thickness of insulation

Additional Formulas Involving British Thermal Unit

Kinetic Energy: The energy of an object in motion is known as kinetic energy, calculated by the formula: KE=1/2 mv² Where:

  • KE is the kinetic energy in British Thermal Unit,
  • m is the mass of the object in kilograms (kg),
  • v is the velocity of the object in meters per second (m/s).

Potential Energy:The potential energy formula involving British thermal units (BTUs) is not typically defined in the same way as it is in classical mechanics, where potential energy is associated with the position of an object relative to a reference point.In this context, calculated by using the formula: PE = MxCxΔT Where:

  • Mass is (M) the mass of the substance.
  • Specific Heat (C) is the specific heat capacity of the substance.
  • ΔTemperature is the change in temperature of the substance

SI multiples of British Thermal Unit (BTU)

PrefixSymbolMultiplication Factor (BTU)

Conversion of British Thermal Unit into other Units

From/ToConversion FactorExample
British Thermal Unit (BTU) to Joule (J)1 BTU = 1055.06 J1 BTU = 1055.06 Joules
British Thermal Unit (BTU) to Calorie (cal)1 BTU = 252.164 cal1 BTU = 252.164 calories
British Thermal Unit (BTU) to Kilowatt-hour (kWh)1 BTU = 0.000293 kWh1 BTU = 0.000293 kilowatt-hours
British Thermal Unit (BTU) to Electronvolt (eV)1 BTU = 6.585×10¹⁵ eV1 BTU = 6.585×10¹⁵ electronvolts
British Thermal Unit (BTU) to Watt-hour (Wh)1 BTU = 0.293071 Wh1 BTU = 0.293071 watt-hours
British Thermal Unit (BTU) to Megajoule (MJ)1 BTU = 1.05506 MJ1 BTU = 1.05506 megajoules
British Thermal Unit (BTU) to Gigajoule (GJ)1 BTU = 1.05506 × 10⁻⁶ GJ1 BTU ≈ 1.05506×10⁻⁶ gigajoules


  • British Thermal Units (BTU) is a unit of energy used primarily in the United States and United Kingdom.
  • It is defined as the amount of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit at a specific temperature.
  • BTU is commonly used to measure the heating or cooling capacity of appliances such as furnaces, air conditioners, and refrigerators.
  • 1 BTU is approximately equal to 1055.06 joules, 252.164 calories, or 0.000293 kilowatt-hours.
  • BTU is also used in various industries such as HVAC (heating, ventilation, and air conditioning), energy production, and building construction.

British Thermal Unit (BTU) to Joule (J)

1 BTU = 1055.06 J

Convert BTUs to Joules, the standard unit of energy in the International System of Units (SI).

British Thermal Unit (BTU) to Calorie (cal)

1 BTU = 252.164 cal

Convert BTUs to Calories, commonly used in nutrition and thermal energy calculations.

British Thermal Unit (BTU) to Kilowatt-hour (kWh)

1 BTU = 0.000293 kWh

Convert BTUs to Kilowatt-hours, a measure of electrical energy consumption.

British Thermal Unit (BTU) to Electronvolt (eV)

1 BTU = 6.585×10156.585×10¹⁵ eV

Convert BTUs to Electronvolts, a unit of energy commonly used in atomic and particle physics.

British Thermal Unit (BTU) to Watt-hour (Wh)

1 BTU = 0.293071 Wh

Convert BTUs to Watt-hours, another measure of electrical energy commonly used in households and industries.

British Thermal Unit (BTU) to Megajoule (MJ)

1 BTU = 1.05506 MJ

Convert BTUs to Megajoules, a unit of energy used in engineering and thermodynamics.

British Thermal Unit (BTU) to Gigajoule (GJ)

1 BTU = 1.05506 × 10⁻⁶ GJ

Convert BTUs to Gigajoules, a larger unit of energy commonly used in the energy industry and power generation.

Practical Application Example

For instance, when selecting an air conditioner for a room, the BTU rating indicates how much heat the unit can remove from the air per hour. A higher BTU rating typically means the air conditioner has a greater cooling capacity and can effectively cool larger spaces.

In residential or commercial buildings, understanding the BTU requirements helps in choosing HVAC systems that are appropriately sized for the space, ensuring optimal comfort and energy efficiency.

Advantages of British Thermal Unit (BTU)?

Scientific Research and Experiments

  • Thermodynamics Studies: BTUs are pivotal in researching heat transfer, phase transitions, and thermal equilibrium.
  • Material Science Investigations: BTU measurements aid in assessing thermal properties of materials like conductivity and specific heat.

Engineering and Technology

  • HVAC System Design: Engineers use BTUs to size heating and cooling systems for buildings based on thermal load calculations.
  • Industrial Processes: BTU measurements guide the design and optimization of industrial heating and cooling systems for manufacturing processes.

Everyday Applications

  • Home Heating and Cooling: BTUs determine the size and efficiency of furnaces, air conditioners, and space heaters for residential comfort.
  • Cooking and Food Industry: BTU ratings help consumers select stoves, ovens, and grills, while food manufacturers use BTUs to control cooking processes and ensure food safety.

Environmental and Energy Sectors

  • Energy Consumption Analysis: BTUs quantify energy usage in residential, commercial, and industrial sectors, aiding in energy efficiency assessments and environmental impact studies.
  • Renewable Energy Systems: BTUs play a role in evaluating the efficiency of renewable energy sources like biomass and solar thermal systems

Education and Research

  • Academic Curricula: BTUs are integral to thermodynamics courses, providing students with fundamental knowledge of heat transfer and energy systems.
  • Experimental Studies: Researchers utilize BTU measurements in laboratory experiments to investigate heat exchange phenomena and develop thermal engineering solutions.

Health and Safety

  • Indoor Air Quality: BTUs influence HVAC system design to maintain optimal indoor temperatures, humidity levels, and air circulation, supporting occupant health and comfort.
  • Fire Safety: Understanding BTUs aids in assessing the fire risk associated with heating appliances and industrial processes

Examples of Joule Units

Mechanical Work:

  • Lifting a 1-kilogram weight by 1 meter against gravity requires approximately 9.81 joules of work.
  • Pushing a box with a force of 1 newton for a distance of 1 meter also results in 1 joule of work done.

Electrical Energy:

  • A 100-watt light bulb consumes 100 joules of electrical energy every second it is turned on.
  • Charging a smartphone battery with a capacity of 2000 milliampere-hours (mAh) from 0% to 100% requires approximately 7.2 kilojoules of energy, or 7200 joules.

Thermal Energy:

  • Heating 1 gram of water by 1 degree Celsius requires approximately 4.184 joules of thermal energy, known as the specific heat capacity of water.
  • Boiling 1 kilogram of water from room temperature (about 20°C) to its boiling point (100°C) requires approximately 79,400 joules of thermal energy.

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