There is no universal square-foot rule for sizing an air conditioner; the official standard is a Manual J load calculation.
For the full breakdown, see our best Air Conditioner For 100 Sq Ft Room guide.
The 1,000-square-foot-to-2-ton rule gets quoted like gospel, but nobody can give a fixed figure for air conditioner size per square foot, because the house decides the number. Climate, insulation, windows, ceiling height, and sun exposure all move the load, which is why the industry’s official method is a Manual J calculation rather than a floor plan. The chart below is a reasonable starting point; the steps after it get you to an exact size.
Square-Foot Shortcuts: Where They Hold Up
Square-foot charts are fine for a first guess, and nothing more.
The most common whole-home shortcut runs about 600 square feet per ton:
- 1,000 sq ft → about 2 tons (24,000 BTU)
- 1,500 sq ft → about 3 tons (36,000 BTU)
- 2,000 sq ft → about 4 tons (48,000 BTU)
- 2,500 sq ft → about 5 tons (60,000 BTU)
Single rooms need more capacity per square foot than whole houses do, because small spaces carry more exterior wall per square foot. Frigidaire’s room air conditioner size guide cites ranges that run from roughly 33 BTU per square foot in a 150 sq ft room down to about 18 BTU per square foot at 1,000 sq ft, and it warns that no fixed number exists.
| Room Size (sq ft) | Recommended Capacity (BTU) |
|---|---|
| 100–150 | 5,000 |
| 150–250 | 6,000 |
| 250–300 | 7,000 |
| 300–350 | 8,000 |
| 350–400 | 9,000 |
| 400–450 | 10,000 |
| 450–550 | 12,000 |
| 550–700
Send us your feedback Tell us what you thought about this post — we read every note. |