Short answer
A 1.5 ton (18,000 BTU) AC cools roughly 900 sq ft in a temperate climate — about 720 sq ft in a hot climate up to 1,000 sq ft in a cooler one. Insulation, ceiling height, sun, and occupancy shift the real figure.
Capacity
18,000 BTU
Typical room
900 sq ft
Hot climate
720 sq ft
Cool climate
1,000 sq ft
A 1.5 ton air conditioner is 18,000 BTU (tonnage is just BTU ÷ 12,000). At the ~20 BTU/sq-ft baseline that covers about 900 square feet in a temperate climate — roughly 720 sq ft where summers are hot, up to 1,000 sq ft in a cooler climate.
Insulation, ceiling height, sun exposure, and how many people use the room all shift the real figure. An oversized unit short-cycles and leaves the room humid, so match the capacity to the space rather than over-buying.
| Factor | Effect on the load |
|---|---|
| Floor area | ~20 BTU per sq ft cooling baseline (ENERGY STAR, 8-ft ceiling) |
| Climate zone | -15% (cold) to +25% (hot) on the cooling load |
| Insulation | Poor +15%, average no change, good -10% |
| Ceiling height | Scales with height ÷ 8 ft — a 10-ft ceiling adds ~25% |
| Sun exposure | Shaded -10% to sunny +10% |
| Occupancy & use | +600 BTU per person over two; +4,000 BTU for a kitchen |
| Climate zone | Area a 18,000 BTU unit cools |
|---|---|
| Hot (e.g. Phoenix, Miami) | ~720 sq ft |
| Warm (e.g. Dallas, Atlanta) | ~820 sq ft |
| Temperate (e.g. St. Louis) | ~900 sq ft |
| Cool (e.g. Chicago, Boston) | ~1,000 sq ft |
| Cold (e.g. Minneapolis) | ~1,060 sq ft |
Temperate (highlighted) is the baseline; insulation, ceiling height, sun, and occupancy shift the real coverage.
Real, widely available units in the 12,000 – 24,000 BTU class. Independent picks — we're not affiliated with any manufacturer or retailer and earn nothing from these links. Always match the unit's BTU to the size above.
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A 1.5 ton unit is 18,000 BTU and cools about 900 sq ft in a temperate climate — roughly 720–1,000 sq ft depending on climate, insulation, and sun.
18,000 BTU. Air-conditioner tonnage is just BTU ÷ 12,000, so 1.5 × 12,000 = 18,000 BTU.
An oversized AC short-cycles — it cools fast but leaves the room humid and wastes energy. If your room is well under 720 sq ft, size down. Enter your room in the calculator to check.