BTU Calculator
Estimate the BTU/h needed to heat or cool a space by area, climate and occupancy.
Runs 100% in your browser — nothing is uploaded.
Result
Formula
BTU/h ≈ area × climate factor (20–30) + 400 BTU per extra person.
About this calculator
Estimate the heating or cooling capacity, in BTU/h, needed to keep a room comfortable based on its area, climate, and the number of people usually present. The calculator multiplies the room area by a climate factor (20 BTU/sq ft for mild, 25 for moderate, 30 for hot/cold) to account for the base heating or cooling load.
How to use
- 1
Enter the room area in square feet.
- 2
Select the climate type (mild, moderate, or hot/cold).
- 3
Enter the number of people usually present, then view the recommended BTU/h and kW.
Frequently asked questions
What does BTU stand for?
BTU stands for British Thermal Unit. It is a unit of energy. In heating and cooling, BTU/h (BTU per hour) measures the rate of heat transfer, indicating the capacity of an air conditioner or heater.
How do I choose the right BTU rating for my room?
Use this calculator to get an estimate based on room area, climate, and occupancy. Then consider other factors like ceiling height, insulation, sun exposure, and appliances. For precise sizing, especially for new installations, consult an HVAC professional.
What happens if I oversize or undersize my air conditioner?
Oversizing can cause short cycling, leading to poor dehumidification and temperature swings. Undersizing means the unit runs continuously and may not reach the desired temperature on hot days. Proper sizing is key for efficiency and comfort.
Please note: Results are estimates for general information only and are not professional or medical/financial advice.