AC Tonnage Calculator
Find the right air conditioner size for any room — enter dimensions and sun exposure to get BTU per hour and tonnage. Avoid an undersized or wasteful unit.
🔄 Updated October 16, 2026
About the AC Tonnage Calculator
The AC Tonnage Calculator is one of our handy everyday tools. Find the right air conditioner size for any room — enter dimensions and sun exposure to get BTU per hour and tonnage. Avoid an undersized or wasteful unit. It works entirely in your browser, free forever. Also popular: the Unit Converter and Random Number Generator.
How to use this calculator
- Enter your numbers in the fields above.
- Results update instantly — no button to press, no page reload.
- Adjust the inputs to compare scenarios with the AC Tonnage Calculator.
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Frequently asked questions
How is tonnage estimated?
Roughly 1 ton per 400 sq ft of floor area, adjusted up 10% for sunny rooms and down 10% for shaded rooms.
What does 1 ton of cooling mean?
12,000 BTU per hour — the heat needed to melt one ton of ice in 24 hours.
Should I oversize my AC?
No — an oversized unit cools too fast, dehumidifies poorly and wastes electricity.