BTU calculator: what size air conditioner do I need?
Enter the room's square footage. We use ENERGY STAR's room air conditioner chart and its adjustments for sun, shade, extra people and kitchens.
Air conditioner size chart
| Area to cool | Capacity needed |
|---|---|
| 100 to 150 sq ft | 5,000 BTU/hr |
| 150 to 250 sq ft | 6,000 BTU/hr |
| 250 to 300 sq ft | 7,000 BTU/hr |
| 300 to 350 sq ft | 8,000 BTU/hr |
| 350 to 400 sq ft | 9,000 BTU/hr |
| 400 to 450 sq ft | 10,000 BTU/hr |
| 450 to 550 sq ft | 12,000 BTU/hr |
| 550 to 700 sq ft | 14,000 BTU/hr |
| 700 to 1,000 sq ft | 18,000 BTU/hr |
| 1,000 to 1,200 sq ft | 21,000 BTU/hr |
| 1,200 to 1,400 sq ft | 23,000 BTU/hr |
| 1,400 to 1,500 sq ft | 24,000 BTU/hr |
| 1,500 to 2,000 sq ft | 30,000 BTU/hr |
| 2,000 to 2,500 sq ft | 34,000 BTU/hr |
ENERGY STAR chart, assuming 8-foot ceilings. Heavily shaded: −10%. Very sunny: +10%. More than two people: +600 BTU each. Kitchen: +4,000 BTU.
Why the right size matters
An oversized unit cools the air quickly and shuts off before it pulls out much moisture, so the room feels clammy; an undersized one runs nonstop and never catches up. For central air and heat pumps, the answer comes from a room-by-room Manual J load calculation by a contractor; rules of thumb tend to oversize. More in what size air conditioner do I need.