Updated
Home & HVAC
BTU Calculator
Estimate heating or cooling capacity in BTU/hr with practical adjustments for ceiling height, insulation, sun exposure, windows, occupancy, and climate. Convert to tons and kW, and total multiple rooms.
Room Capacity Estimator with Tons & kW Output
Choose cooling or heating, enter your room details, and get a recommended capacity range with clear conversions and sizing notes.
Cooling results are estimated for planning. If you are between sizes, choose comfort goals: humid climates often benefit from avoiding oversizing to reduce short cycling and improve moisture removal.
Heating estimates depend heavily on building envelope and infiltration. If you feel drafts or have older windows, the required BTU/hr can increase quickly.
Add rooms, then calculate a total BTU/hr. Use this for quick whole-home planning or to estimate total capacity for multiple zones.
| Room | Area | Sun | Windows | People | BTU/hr | Remove |
|---|
Conversions use common engineering constants: 1 ton = 12,000 BTU/hr and 1 kW ≈ 3,412.142 BTU/hr. BTU to BTU/hr depends on the time period.