QuickCheckToolsBTU calculator
Find the right air conditioner size for your room, using the ENERGY STAR sizing chart and its adjustments for sun, shade, occupants and kitchens.
ENERGY STAR room air conditioner sizing chart
| Room size | 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 |
Then adjust: −10% if heavily shaded, +10% if very sunny, +600 BTU for each regular occupant beyond two, and +4,000 BTU in a kitchen.
Questions
How many BTUs do I need for my room?
Multiply the room's length by its width to get square feet, then use the ENERGY STAR chart: for example, 150 to 250 square feet needs 6,000 BTUs and 400 to 450 needs 10,000. Then adjust for sun, shade, occupants and kitchens.
How many BTUs for a 12x12 room?
A 12 x 12 room is 144 square feet, which falls in the 100–150 band, so it needs a 5,000 BTU air conditioner before any adjustments.
Is a bigger air conditioner better?
No. ENERGY STAR notes that an oversized unit cools the room too quickly without removing enough moisture, leaving it damp and clammy, and wastes energy. Choose the size that matches your room.
What adjustments should I make?
Reduce capacity by 10% for a heavily shaded room and increase it by 10% for a very sunny one. Add 600 BTUs for each person beyond two who regularly uses the room, and add 4,000 BTUs if the unit is in a kitchen.
How do I measure a room with inches?
Convert inches to part of a foot: 12 feet 6 inches is 12.5 feet. Then multiply length by width.
What if my room is bigger than 2,500 square feet?
The ENERGY STAR room air conditioner chart stops at 2,500 square feet. Larger spaces usually need central air or several units, so it's worth asking an HVAC professional to size the system.
Sizing chart and adjustments from ENERGY STAR (US Environmental Protection Agency). For whole-home or unusual spaces, ask an HVAC professional.