BTU Calculator
Size an air conditioner for a room. Enter the room dimensions, how much sun it gets, and how many people use it to get the recommended cooling capacity in BTU and tons.
Your project
Estimate
Recommended cooling · Air conditioner capacity
- In tons
- 0.5tons
- Room area
- 300ft²
Estimates are guidance only and exclude tax, labor, and site conditions unless stated. Confirm with a local pro.
How it's calculated
No black boxes — here is the exact math behind your estimate, so you can check it or adapt it for your own quote.
- 1
Room area (ft²) = length × width - 2
Base BTU = area × 20 BTU/ft² - 3
Adjusted BTU = base BTU × sun factor - 4
Add 600 BTU for each occupant beyond two - 5
Tons = BTU ÷ 12,000
Worked example
A 15 ft × 20 ft living room with average sun and 2 occupants.
Inputs
- Room length
- 15 ft
- Room width
- 20 ft
- Sun exposure
- 1
- Regular occupants
- 2
Result
- Recommended cooling
- 6,000 BTU
- In tons
- 0.5 tons
- Room area
- 300 ft²
Tools & materials for this project
As an Amazon Associate we may earn from qualifying purchases, at no extra cost to you.
- Window air conditioner Cools a single room sized to your BTU result.
- Portable air conditioner No-install cooling for rooms without a window mount.
- Mini split AC Efficient cooling and heating for a room or zone.
Compare local pros for btu
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