BTU Calculator
Multiply room area by an assumed BTU-per-square-foot factor.
This calculator is free to use. Enable JavaScript to enter your values and see a result instantly.
How it works
Multiply room area by an assumed BTU-per-square-foot factor.
Worked example
400 square feet at 20 BTU per square foot suggests 8,000 BTU/h.
Keep in mind
Sun exposure, climate, insulation, and occupancy affect real sizing.