Your AC
Room Size Guide
A 1.5 ton AC removes 18,000 BTU of heat per hour — always, everywhere. What changes by climate is how fast heat enters the room per square foot. In the UK at peak summer (around 20°C), about 25 BTU enters each square foot per hour. In the Gulf at peak summer (above 45°C), about 100 BTU enters each square foot per hour. The 1.5 ton AC must work against four times as much incoming heat per square foot, so it can cover only one quarter of the floor area.
| AC Size | Very Hot (>40°C) | Hot (33–40°C) | Warm (27–33°C) | Temperate (20–27°C) | Cool (<20°C) |
|---|---|---|---|---|---|
| 0.75 ton | 90 sqft / 8 m² | 120 sqft / 11 m² | 180 sqft / 17 m² | 257 sqft / 24 m² | 360 sqft / 33 m² |
| 1 ton | 120 sqft / 11 m² | 160 sqft / 15 m² | 240 sqft / 22 m² | 343 sqft / 32 m² | 480 sqft / 45 m² |
| 1.5 ton | 180 sqft / 17 m² | 240 sqft / 22 m² | 360 sqft / 33 m² | 514 sqft / 48 m² | 720 sqft / 67 m² |
| 2 ton | 240 sqft / 22 m² | 320 sqft / 30 m² | 480 sqft / 45 m² | 686 sqft / 64 m² | 960 sqft / 89 m² |
| 2.5 ton | 300 sqft / 28 m² | 400 sqft / 37 m² | 600 sqft / 56 m² | 857 sqft / 80 m² | 1,200 sqft / 111 m² |
The maximum is the largest room the AC can maintain at the set temperature on a peak-design-day. The ideal range (65–100% of the maximum) is where the unit runs most efficiently — long enough cycles to remove humidity properly, short enough to maintain temperature without overcooling. Rooms within the ideal range will feel the most comfortable year-round.
For rooms where the required area exceeds 24,000 BTU (2 ton) in a hot or very hot climate, a single wall-mounted split AC is approaching its practical residential limit. Two smaller units positioned to cover different halves of the room, or a cassette-type unit mounted in the ceiling centre that distributes cooling in four directions, will deliver more even cooling for large rooms.
What room size can a 1.5 ton AC handle?
Cool climate (UK): up to ~720 sq ft (67 m²). Temperate (N. USA, C. Europe): up to ~510 sq ft (47 m²). Hot (S. Asia, SE Asia): up to ~240 sq ft (22 m²). Very Hot (Gulf): up to ~180 sq ft (17 m²).
How do I know if my AC is too small?
The room never reaches the set temperature on peak days, the compressor runs without cycling off, and far corners stay warm while the area near the unit is cool. Enter your AC size and climate above — if your room exceeds the maximum shown, the unit is undersized.
Can one AC cool two connected rooms?
Yes, if the combined area does not exceed the maximum for the AC in your climate, and there is an unrestricted opening between rooms for airflow. Add both areas together and check the result above.
Why does the same AC handle very different sizes by country?
The rate of heat entering per square foot is vastly different. UK (20°C peak): ~25 BTU/sqft. Gulf (45°C peak): ~100 BTU/sqft. The AC removes the same 18,000 BTU/hr either way — it covers far fewer sq ft when each foot contributes four times more heat.
Does a top-floor room reduce the effective room size?
Yes. An uninsulated top-floor room has 25–40% more heat load per sq ft, so the same AC handles 25–40% less floor area. A 1.5 ton AC handling 240 sq ft on a middle floor can only handle about 185 sq ft on an uninsulated top floor in a hot climate.
Room size ranges are based on the climate zone and conditions you select. Actual capacity varies with ceiling height, insulation, and specific unit performance.