Free tool · HVAC technical
BTU calculator (room and home sizing)
Quick cooling load estimate by area, climate, sun and occupants. Not a Manual J.
Estimated cooling capacity
10,000 BTU/h
In tons
0.83 tons
1 ton = 12,000 BTU/h
A quick estimate, not a load calculation. Based on Energy Star's room air conditioner sizing method. For whole-home equipment selection, run an ACCA Manual J load calculation.
How it works
This uses Energy Star's room air conditioner sizing method: a capacity from the floor area, adjusted for sun, people and kitchens. It's useful for room units, mini-split zones and quick conversations.
It is not a load calculation. Whole-home equipment should be sized with an ACCA Manual J, which accounts for insulation, windows, orientation, infiltration and local design temperatures.
The formula
Base capacity from Energy Star's area table; −10% for heavy shade, +10% for very sunny rooms; +600 BTU/h per regular occupant above two; +4,000 BTU/h for a kitchen. 12,000 BTU/h = 1 ton.
Frequently asked questions
For a single room, Energy Star's table works out to roughly 20 BTU per square foot for typical rooms, adjusted for sun, people and kitchens. For whole homes, the answer varies widely with climate and construction: run a Manual J.
Sources
Last reviewed October 15, 2026. Third-party sources are marked; some are written by competing vendors.
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