BTU Calculator
Estimate the required AC/heating BTU capacity from room area, ceiling height, sunlight and occupancy.
Input Data
Results
4,400
At a glance:Baseline ~20 BTU per sq ft, scaled by ceiling height (above 8 ft), multiplied by a sunlight factor (low 1.0 / avg 1.1 / high 1.25), then +400 BTU per person.
Formula
sunMult = low 1.0 / avg 1.1 / high 1.25.
baseBtu = area × 20 × (ceiling ÷ 8) × sunMult + people × 400.
How to Use
- Enter room area, ceiling height and sunlight level.
- Enter the number of occupants to get the recommended BTU.
FAQ
Why 20 BTU per sq ft?
It is a common industry rule of thumb for typical homes; actual needs also depend on windows, insulation and climate.
How do I pick a unit from this?
Choose the closest capacity tier and leave about 10–20% headroom for extreme weather.
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References
Content reviewed by the Calculatorism editorial team. Results are for reference only; please refer to the relevant authorities for the official figures.