Find the air-conditioner capacity in BTU/h and tons that suits your room.
Match capacity to floor area using the ENERGY STAR chart, then adjust for height, sun and people. A 180 sq ft (17 m²) room needs about 6,000 BTU/h; make it sunny with 4 people and it rises to 7,800 BTU/h. One ton of cooling is 12,000 BTU/h.
The AC BTU Calculator estimates the cooling capacity a room needs. Enter the room's length, width and ceiling height, then describe the sun exposure and how many people use it. It returns the capacity in BTU per hour, watts and tons, the nearest standard air-conditioner size and the next common tonnage up.
An undersized AC runs constantly and never cools the room; an oversized one cycles on and off, cools unevenly and removes less humidity. Use this as a sizing guide and ask a professional for a full load calculation for large or unusual spaces. See the Electricity Calculator to estimate running cost.
The method follows the ENERGY STAR room air conditioner guidance.
| Room | Capacity needed | Nearest size |
|---|---|---|
| 12 × 12 ft (144 sq ft), 8 ft ceiling | 5,000 BTU/h | 5,000 BTU/h (about 0.42 tons) |
| 15 × 12 ft, sunny, 4 people | 7,800 BTU/h | 8,000 BTU/h (about 0.67 tons) |
| 4 × 5 m (20 m²), 2.7 m ceiling | 6,644 BTU/h | 8,000 BTU/h (about 0.67 tons) |
| 20 × 20 ft, 10 ft ceiling, 3 people, top floor | 12,975 BTU/h | 14,000 BTU/h (about 1.17 tons) |
| Room area (sq ft) | Room area (m²) | Capacity (BTU/h) | Approx. tons |
|---|---|---|---|
| 100 to 150 | 9 to 14 | 5,000 | 0.4 |
| 150 to 250 | 14 to 23 | 6,000 | 0.5 |
| 250 to 300 | 23 to 28 | 7,000 | 0.6 |
| 300 to 350 | 28 to 33 | 8,000 | 0.7 |
| 350 to 400 | 33 to 37 | 9,000 | 0.75 |
| 400 to 450 | 37 to 42 | 10,000 | 0.8 |
| 450 to 550 | 42 to 51 | 12,000 | 1.0 |
| 550 to 700 | 51 to 65 | 14,000 | 1.2 |
| 700 to 1,000 | 65 to 93 | 18,000 | 1.5 |
| 1,000 to 1,200 | 93 to 111 | 21,000 | 1.75 |
| 1,200 to 1,400 | 111 to 130 | 23,000 | 1.9 |
| 1,400 to 1,500 | 130 to 139 | 24,000 | 2.0 |
| 1,500 to 2,000 | 139 to 186 | 30,000 | 2.5 |
| 2,000 to 2,500 | 186 to 232 | 34,000 | 2.8 |
A note on climate: the ENERGY STAR chart assumes typical US conditions. In very hot climates such as much of India, installers commonly size one step larger and often quote roughly 1 ton for up to about 120 sq ft and 1.5 tons for about 120–180 sq ft, so treat this calculator's result as a minimum. In India, split and window ACs are sold in 0.75, 1, 1.5, 2 and 2.5 ton sizes. A 1-ton AC delivers 12,000 BTU/h and a 1.5-ton unit 18,000 BTU/h. If your result sits between two sizes, choose the larger for west-facing, top-floor or heavily glazed rooms, and the smaller for well-shaded rooms.
Find your room's area, read the base capacity from the ENERGY STAR chart, then adjust for ceiling height, sun, people and kitchen use. This calculator does that.
12,000 BTU/h equals 1 ton of cooling, 18,000 BTU/h is 1.5 tons and 24,000 BTU/h is 2 tons.
About 5,000–6,000 BTU/h — usually a 0.5–0.75 ton unit, or a 1-ton AC if the room is sunny or on the top floor.
Yes, comfortably. By the ENERGY STAR chart a 200 sq ft room needs about 6,000 BTU/h, but that guidance is for typical US conditions. In India's hot climate retailers often suggest around 1.5 tons for 150–200 sq ft, so a 1.5 ton unit is a sensible choice.
Direct sunlight through windows and walls adds a lot of heat, so a very sunny room needs about 10% more capacity.
Yes — each person beyond two adds about 600 BTU/h of body heat.
Yes. A higher ceiling means more air to cool; capacity scales with height ÷ 8 ft.
No. An oversized AC short-cycles, which cools unevenly, wears the compressor and dehumidifies poorly.
A BTU is a unit of heat energy. AC capacity is measured in BTU per hour, and one ton equals 12,000 BTU/h.
No. Everything runs in your browser.
