BTU Calculator — Air Conditioner Size
Enter room square footage and conditions to calculate the right AC size in BTU.
Calculate the right BTU (British Thermal Unit) capacity for your air conditioner based on your room's square footage, ceiling height, sun exposure, and number of occupants. An undersized AC can't cool the room; an oversized one cycles too often and doesn't dehumidify well.
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Last reviewed: April 2026Report an error
Recommended BTU
7,500 BTU
7,500 BTU/hr needed for 300 sq ft room. 0.63 tons AC. Suggested: 5,000–8,000 BTU.
Recommended BTU
7,500
AC Tonnage
0.63 tons
Suggested Unit
5,000–8,000 BTU
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How to Use This BTU / AC Size Calculator
- Enter room square footage.
- Enter ceiling height.
- Select sun exposure (south-facing rooms need more BTU).
- Enter number of regular occupants.
- Read recommended BTU, AC tonnage, and suggested unit size.
Frequently Asked Questions
- The Energy Star baseline is 20–25 BTU per square foot. Adjust up for sunny/hot rooms, high ceilings, or many occupants; down for shaded rooms.
- 1 ton of AC capacity = 12,000 BTU/hour. A 2,000 sq ft home in a hot climate might need 3–4 tons (36,000–48,000 BTU) for central AC.
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