Cooling · Room sizing
What size AC for a 120 sq ft room?
A 120 sq ft room with 8 ft ceilings needs about 13,592 BTU/h (1.1 tons) of cooling in a hot climate — buy a 15,000 BTU unit, or 18,000 BTU if the room gets direct sun.
By ceiling height
| Ceiling | BTU/h (shaded) | BTU/h (sunny) | Tons |
|---|---|---|---|
| 8 ft | 13,592 | 16,311 | 1.1 |
| 9 ft | 15,291 | 18,349 | 1.3 |
| 10 ft | 16,990 | 20,388 | 1.4 |
Hot-climate volumetric method (500–600 BTU/h per m³) — the same formula as our BTU calculator, where you can enter exact dimensions. In mild climates use the room-size chart's 20–25 BTU/sq ft column instead.
FAQ
- How many BTU for 120 sq ft?
- In a hot climate with 8 ft ceilings: about 13,592 BTU/h shaded, or 16,311 BTU/h with direct sun. In a mild climate the 20–25 BTU/sq ft rule gives 2,400–3,000 BTU/h — use that as the floor for insulated rooms.
- How many tons is that?
- 13,592 BTU/h equals 1.1 tons of cooling (1 ton = 12,000 BTU/h) — about 4 kW.