HVAC BTU Calculator
Estimate cooling BTU from room size, insulation, sun, occupants, and kitchen, plus heating BTU by climate zone.
Processed locally in your browser — nothing is uploaded.
+600 BTU per person beyond 2
Enter the room area to estimate BTU.
About HVAC BTU Calculator
The cooling estimate starts from the common 20 BTU per square foot rule, scales for ceiling height, insulation quality, and sun exposure, then adds 600 BTU per occupant beyond two and 4,000 BTU for a kitchen. Heating uses a climate-zone rate from 30 (hot climates) to 60 BTU/sq ft (very cold).
Common uses
- Pick a window or portable AC size for a bedroom
- Get a ballpark furnace or mini-split heating load by climate
Example
Input
300 sq ft, 8 ft ceiling, average insulation, 4 people, kitchen
Output
11,200 BTU/hr cooling · 12,000 BTU/hr heating (zone 4)
Limitations
- Rule-of-thumb sizing only — a Manual J calculation is the real standard for installed equipment
- Windows, air sealing, and ductwork are not modeled