Square feet per ton
One ton of cooling is 12,000 BTU/h. A rough rule is one ton per 400–600 ft² of living space, with hot climates at the low end of the range and cool climates at the high end. This calculator uses these BTU per ft² values for average insulation:
| IECC climate zone | BTU/h per ft² | ft² per ton |
|---|---|---|
| Zones 1–2 (hot) | 30 | 400 |
| Zone 3 (warm) | 25 | 480 |
| Zone 4 (mixed) | 22 | 545 |
| Zones 5–7 (cool) | 18 | 667 |
Worked example
A 1,800 ft² house in zone 4 with average insulation: 1,800 × 22 = 39,600 BTU/h = 3.3 tons. The next standard size is a 3.5-ton system.
Why a Manual J matters
Square-foot rules ignore window area, orientation, duct leaks and the local design temperature. Many existing homes turn out oversized when a proper ACCA Manual J load calculation is done, so use this number for budgeting and ask your contractor for a Manual J before buying.
Frequently asked questions
What size AC do I need for a 2,000 sq ft house?
Roughly 3 to 5 tons depending on climate: about 3 tons in a cool zone (18 BTU/ft²) and 5 tons in a hot zone (30 BTU/ft²) with average insulation.
How many square feet does a 3-ton AC cool?
About 1,200 ft² in a hot climate up to about 2,000 ft² in a cool climate, with average insulation.