HVAC
BTU Calculator
Estimate the BTU output needed to heat or cool any room based on size, insulation, and climate.
These are estimates based on general rules of thumb. A proper Manual J load calculation accounts for wall construction, window types, ductwork, and local design temperatures. Always run Manual J before sizing equipment for a customer.
Common Questions
How many BTU do I need to heat a room?
A rough starting point is 20 BTU per square foot for heating in moderate climates. A 500 square foot room needs about 10,000 BTU. Adjust up for cold climates, poor insulation, high ceilings, or lots of windows.
How do I size an AC unit for a room?
For cooling, use 20 to 25 BTU per square foot depending on sun exposure and climate. A 1,000 square foot area typically needs an 18,000 to 24,000 BTU unit, which is 1.5 to 2 tons.
What is the difference between BTU and tons for HVAC?
One ton of cooling equals 12,000 BTU per hour. A 2 ton AC unit produces 24,000 BTU. Residential systems range from 1.5 to 5 tons depending on home size and climate.
Does ceiling height affect BTU calculations?
Yes. Standard calculations assume 8 foot ceilings. For every foot above 8 feet, add roughly 10 percent more BTU. A room with 10 foot ceilings needs about 25 percent more capacity than the same room with 8 foot ceilings.
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