Room size → BTU, tonnage & unit type
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.
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.
Best overall
12k / 18k / 24k BTU
Ductless mini-split · heat pump · Cools + heats · strong all-rounder
A consistent independent favorite — efficient inverter heat pump that both cools in summer and heats in winter, at a mid-market price.
Find on AmazonBest value
12k / 18k / 24k BTU
Ductless mini-split · DIY · Pre-charged quick-connect · warranty holds on self-install
The only mainstream line with true pre-charged quick-connect line sets, so a homeowner can install it without a vacuum pump — and keep the full warranty.
Find on AmazonBudget pick
12k / 18k / 24k BTU
Ductless mini-split · Lowest entry price in the class
The budget way into a ductless heat pump. Field-charging and a licensed install get you the longer warranty.
Find on AmazonMini-splits mount permanently and need a small wall penetration; DIY kits are homeowner-installable, others want an HVAC tech.
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.