BTU Calculator

Estimate a room's heating or cooling capacity from area and simple adjustment factors.

Approximate capacity

8,000 BTU/h

0.7 tons of cooling

Room area400 sq ft

Insulation factor1×

Sun exposure factor1×

Occupants2

Rule-of-thumb sizing only. Proper HVAC sizing requires climate, windows, ceiling height, air leakage, and a professional load calculation.

About the BTU Calculator

Estimate a room's heating or cooling capacity from area and simple adjustment factors.

It runs entirely in your browser — nothing you type is sent to a server — and the result updates as you edit the inputs. Estimates are for educational and informational purposes only; see ourdisclaimer.

Common searches

hvac sizing
air conditioner
heating

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