BTU calculator (air conditioner)
Find out how many BTUs your air conditioner needs for your room, from the area, number of people, appliances and afternoon sun.
How many BTUs do I need?
Everything happens on your device: nothing is uploaded to the internet.
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BTU calculator (air conditioner): what it is for
Enter the area of the room, how many people usually stay in it and how many appliances give off heat. The calculator applies the rule of 600 BTU per square meter (800 with afternoon sun) and points to the nearest standard model, from 7,000 to 60,000 BTU.
The table shows each part of the calculation so you can check it.
How to use
- Type the room area.
- Enter people and appliances.
- Check if it gets afternoon sun and see the model.
When to use it
- Buy the right air conditioner for a bedroom.
- Size the cooling for an office.
- Check a store's recommendation.
Frequently asked questions
How do I calculate air conditioner BTUs?
The most common rule is 600 BTU per square meter (about 55 BTU per square foot) for up to 2 people, plus 600 BTU for each extra person and for each heat-producing appliance, like a TV or computer. If the room gets afternoon sun, use 800 BTU per square meter.
What if the result falls between two models?
Choose the next size up. A unit that is too small runs nonstop, uses more energy and doesn't cool properly.
Does a high ceiling change the calculation?
Yes. The rule applies to ceilings up to about 2.7 m (9 ft). For taller rooms, rooms with many windows or kitchens, ask an installer.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.