How the tables are made: for each size, every chart row is tried with ENERGY STAR's adjustments, as the BTU calculator applies them (10 percent less for a heavily shaded room, 10 percent more for a very sunny one, 600 BTU/h for each person over two). The answer is the largest row whose need is not more than the size. We assume an 8 ft ceiling, the height ENERGY STAR says its capacities are based on.
How many square feet does each AC size cool?
A 12,000 BTU/h air conditioner covers a room up to 550 sq ft on the ENERGY STAR room chart when the room has average sun and two people, but only 450 sq ft when the room is very sunny. The tables below read the chart backwards for each common window and portable unit size: the largest room it covers when shaded, average or sunny, and with three or four people.
Updated
Two people or fewer in the room
| Unit size | Heavily shaded | Average | Very sunny |
|---|---|---|---|
| 5,000 BTU/h | 150 sq ft (13.9 m²) | 150 sq ft (13.9 m²) | smaller than the chart |
| 6,000 BTU/h | 250 sq ft (23.2 m²) | 250 sq ft (23.2 m²) | 150 sq ft (13.9 m²) |
| 8,000 BTU/h | 350 sq ft (32.5 m²) | 350 sq ft (32.5 m²) | 300 sq ft (27.9 m²) |
| 10,000 BTU/h | 450 sq ft (41.8 m²) | 450 sq ft (41.8 m²) | 400 sq ft (37.2 m²) |
| 12,000 BTU/h | 550 sq ft (51.1 m²) | 550 sq ft (51.1 m²) | 450 sq ft (41.8 m²) |
| 14,000 BTU/h | 700 sq ft (65.0 m²) | 700 sq ft (65.0 m²) | 550 sq ft (51.1 m²) |
| 18,000 BTU/h | 1,000 sq ft (92.9 m²) | 1,000 sq ft (92.9 m²) | 700 sq ft (65.0 m²) |
| 24,000 BTU/h | 1,500 sq ft (139.4 m²) | 1,500 sq ft (139.4 m²) | 1,200 sq ft (111.5 m²) |
Three people in the room
| Unit size | Heavily shaded | Average | Very sunny |
|---|---|---|---|
| 5,000 BTU/h | smaller than the chart | smaller than the chart | smaller than the chart |
| 6,000 BTU/h | 250 sq ft (23.2 m²) | 150 sq ft (13.9 m²) | smaller than the chart |
| 8,000 BTU/h | 350 sq ft (32.5 m²) | 300 sq ft (27.9 m²) | 250 sq ft (23.2 m²) |
| 10,000 BTU/h | 450 sq ft (41.8 m²) | 400 sq ft (37.2 m²) | 350 sq ft (32.5 m²) |
| 12,000 BTU/h | 550 sq ft (51.1 m²) | 450 sq ft (41.8 m²) | 450 sq ft (41.8 m²) |
| 14,000 BTU/h | 700 sq ft (65.0 m²) | 550 sq ft (51.1 m²) | 550 sq ft (51.1 m²) |
| 18,000 BTU/h | 1,000 sq ft (92.9 m²) | 700 sq ft (65.0 m²) | 700 sq ft (65.0 m²) |
| 24,000 BTU/h | 1,500 sq ft (139.4 m²) | 1,400 sq ft (130.1 m²) | 1,200 sq ft (111.5 m²) |
Four people in the room
| Unit size | Heavily shaded | Average | Very sunny |
|---|---|---|---|
| 5,000 BTU/h | smaller than the chart | smaller than the chart | smaller than the chart |
| 6,000 BTU/h | 150 sq ft (13.9 m²) | smaller than the chart | smaller than the chart |
| 8,000 BTU/h | 300 sq ft (27.9 m²) | 250 sq ft (23.2 m²) | 250 sq ft (23.2 m²) |
| 10,000 BTU/h | 400 sq ft (37.2 m²) | 350 sq ft (32.5 m²) | 350 sq ft (32.5 m²) |
| 12,000 BTU/h | 550 sq ft (51.1 m²) | 450 sq ft (41.8 m²) | 400 sq ft (37.2 m²) |
| 14,000 BTU/h | 700 sq ft (65.0 m²) | 550 sq ft (51.1 m²) | 450 sq ft (41.8 m²) |
| 18,000 BTU/h | 1,000 sq ft (92.9 m²) | 700 sq ft (65.0 m²) | 700 sq ft (65.0 m²) |
| 24,000 BTU/h | 1,500 sq ft (139.4 m²) | 1,200 sq ft (111.5 m²) | 1,000 sq ft (92.9 m²) |
How many square feet does a 12000 BTU AC do?
Up to 550 sq ft (51.1 m²) in an average room with two people: 12,000 BTU/h is the chart's row for 450 up to 550 sq ft. In a very sunny room the need rises by 10 percent, so the same unit covers 450 sq ft; with four people in a sunny room it covers 400 sq ft. A heavily shaded room lowers the need, but the next row up (550 up to 700 sq ft) still needs more than 12,000 BTU/h, so the answer stays 550 sq ft.
Is 7000 BTU enough for a bedroom?
For most bedrooms, yes. On the chart 7,000 BTU/h covers up to 300 sq ft with average sun and two people, and 250 sq ft with three. A 12 × 14 ft bedroom (168 sq ft) needs 6,000 BTU/h.
You may not find a 7,000 BTU/h unit, though. In ENERGY STAR's list of certified room air conditioners (counted on 2026-11-09) no model is rated at exactly 7,000 BTU/h; the common sizes either side are 6,000 and 8,000 BTU/h.
How to calculate BTU needed for room size?
- Measure length and width in feet and multiply: a 14 × 16 ft room is 224 sq ft.
- Find the chart row: 150 up to 250 sq ft needs 6,000 BTU/h.
- Adjust for sun: on ENERGY STAR's rule a very sunny room adds 10 percent, 6,600 BTU/h.
- Add 600 BTU/h for each regular occupant over two, also ENERGY STAR's rule: with three people, 7,200 BTU/h.
- Add 4,000 BTU/h if the room is a kitchen (ENERGY STAR). This example room is not a kitchen, so the need stays 7,200 BTU/h.
- Pick the next common size up: 8,000 BTU/h for a window unit.
The calculator with this example does the same steps and shows them. The rules and the reasons for the order are on How we calculate; to turn a capacity into watts, kilowatts or tons, use the converter.