DIY Cost Tools
HVAC BTU Calculator
PLANNING CALCULATOR
Create a rough heating or cooling capacity estimate from floor area, ceiling height, climate, insulation, occupants, and windows.
How it works
This screening estimate scales a user-selected BTU-per-square-foot baseline for ceiling height, climate, insulation, occupants, and windows. It is not an equipment-sizing calculation.
Formula
Rough BTU/h = area × height factor × base load × climate × insulation + occupant/window adjustments
1 cooling ton = 12,000 BTU/h
Important limits
- Do not purchase HVAC equipment from this estimate alone.
- Professional sizing requires a recognized load calculation such as ACCA Manual J and must consider orientation, construction, infiltration, ducts, humidity, design temperatures, and internal gains.
- Oversized systems can short-cycle and control humidity poorly; undersized systems may not maintain comfort.
Frequently asked questions
What does HVAC tonnage mean?
One nominal cooling ton equals 12,000 BTU per hour of cooling capacity.
Why is this only a rough estimate?
Square footage cannot capture the building envelope, weather design conditions, air leakage, and duct losses needed for proper sizing.
Review notes
This is a transparent planning screen with adjustable assumptions, not a substitute for a professional load calculation. Last reviewed September 30, 2026.