BTU Calculator

Calculate heating and cooling BTU requirements based on room size, insulation, and climate.

Result

Fill in the fields above, then press Calculate.

A BTU calculator estimates the heating or cooling capacity needed for a room based on its size, insulation, sun exposure, and occupancy.

Select heating or cooling mode, enter your room size in square feet, ceiling height, insulation quality, sun exposure, and the number of occupants. The calculator estimates the BTU (British Thermal Units) per hour needed.

Examples

300 sq ft room, cooling

Base: 300 x 20 = 6,000 BTU. With average insulation, medium sun, standard ceiling, and 2 occupants: 6,000 BTU/hr (0.5 tons).

Frequently Asked Questions

What is a BTU?
A British Thermal Unit (BTU) is the amount of energy needed to heat or cool one pound of water by one degree Fahrenheit. Air conditioners and heaters are rated in BTU/hr to indicate their capacity.
How do I convert BTU to tons?
One ton of air conditioning equals 12,000 BTU/hr. Divide the BTU requirement by 12,000 to get the tonnage needed.
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Quick Tips

  • •Oversize your unit slightly rather than undersizing; an undersized system runs constantly and wastes energy.
  • •Have a professional perform a Manual J load calculation for whole-home HVAC sizing.
  • •Consider zoned systems for homes with rooms that have very different heating and cooling needs.