BTU Calculator
How to size an air conditioner
- Choose square feet or square meters and enter the floor area and ceiling height.
- Choose how sunny the room is.
- Enter the number of people and tick Kitchen if it is one.
Frequently asked questions
How is it worked out?
About 20 BTU/h per square foot for an 8 ft ceiling, 10% less for shaded rooms and 10% more for sunny ones, 600 BTU/h for each person beyond two and 4,000 BTU/h for a kitchen.
How many watts is one BTU/h?
About 0.293 W, so 12,000 BTU/h (one ton of cooling) is about 3.5 kW.
What size air conditioner should I buy?
One rated at or a little above the result. An oversized unit cools the room too quickly to dry the air well.
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