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BTU Calculator

The following calculator can be used to estimate the amount of BTU (British thermal unit) needed for the heating or cooling of your house/room based on the size and the temperature change you want to achieve.

Please note that this calculator can only give out a rough estimation based on experience. You should also consider factors like efficiency decrease of the heater or air conditioner with time, the shape/type of your house/room, insulation conditions, etc. 1 watt is approximately 3.41214 BTU/h.

room/house width
room/house length
ceiling height
insulation condition
temperature to increase
or decrease
Depending on your local winter/summer temperature,
e.g. 75F for Boston winter, 35F for Atlanta winter.


Reference

The British Thermal Unit or BTU is an energy unit. It is approximately the energy needed to heat one pound of water for one 1 Fahrenheit. 1 BTU = 1,055 joules. 1BTU/hour = 0.293 watt.

Examples:

  • One well insulated 1,000 square foot house in Boston needs around 24,000 BTU to heat in winter.

  • One 2,000 square foot house with normal insulation condition in Washington D.C. needs a 48,000 BTU air conditioner for cooling in summer.