How big an air conditioner does your room need?
Last updated · Sizing chart: ENERGY STAR
How these numbers are madeReport an error
Enter the room and we'll work out the cooling capacity in BTU using the ENERGY STAR sizing chart, then tell you which common unit size to shop for.
Quick answers from the ENERGY STAR chart
- A 150 sq ft room needs about 5,000 BTU
- A 250 sq ft room needs about 6,000 BTU
- A 300 sq ft room needs about 7,000 BTU
- A 400 sq ft room needs about 9,000 BTU
- A 500 sq ft room needs about 12,000 BTU
- A 1,000 sq ft room needs about 18,000 BTU
- A 10×10 ft room (100 sq ft) needs about 5,000 BTU
- A 10×12 ft room (120 sq ft) needs about 5,000 BTU
- A 12×14 ft room (168 sq ft) needs about 6,000 BTU
- A 15×20 ft room (300 sq ft) needs about 7,000 BTU
Before adjusting for sun, extra people or a kitchen. The calculator below applies those.
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A 224 sq ft room needs about
6,000 BTU
- 5k
- 6k (recommended)
- 8k
- 10k
- 12k
- 14k
- 18k
- 24k
Shop for a unit rated 6,000 BTU, the closest common size at or above your number. Sizes struck through are too small for this room.
See 6,000 BTU window units on AmazonHow the calculator works
It starts from the room's floor area and looks up the matching capacity in the ENERGY STAR room air conditioner chart, then applies the four adjustments ENERGY STAR publishes alongside it.
- Up to 150 sq ft5,000
- 150–250 sq ft6,000
- 250–300 sq ft7,000
- 300–350 sq ft8,000
- 350–400 sq ft9,000
- 400–450 sq ft10,000
- 450–550 sq ft12,000
- 550–700 sq ft14,000
- 700–1,000 sq ft18,000
- 1,000–1,200 sq ft21,000
- 1,200–1,400 sq ft23,000
- 1,400–1,500 sq ft24,000
- 1,500–2,000 sq ft30,000
- 2,000–2,500 sq ft34,000
| Room area | Capacity |
|---|---|
| Up to 150 sq ft | 5,000 BTU |
| 150 to 250 sq ft | 6,000 BTU |
| 250 to 300 sq ft | 7,000 BTU |
| 300 to 350 sq ft | 8,000 BTU |
| 350 to 400 sq ft | 9,000 BTU |
| 400 to 450 sq ft | 10,000 BTU |
| 450 to 550 sq ft | 12,000 BTU |
| 550 to 700 sq ft | 14,000 BTU |
| 700 to 1,000 sq ft | 18,000 BTU |
| 1,000 to 1,200 sq ft | 21,000 BTU |
| 1,200 to 1,400 sq ft | 23,000 BTU |
| 1,400 to 1,500 sq ft | 24,000 BTU |
| 1,500 to 2,000 sq ft | 30,000 BTU |
| 2,000 to 2,500 sq ft | 34,000 BTU |
- Heavily shaded room: reduce capacity by 10%.
- Very sunny room: increase capacity by 10%.
- More than two people: add 600 BTU for each additional person.
- Kitchen: add 4,000 BTU.
The chart is built for single rooms with standard 8-foot ceilings. For vaulted ceilings, open-plan floors, or a whole house, have an HVAC contractor do a Manual J load calculation instead.
Already have an AC that isn't keeping up?
A unit that once cooled the room fine usually has a maintenance problem, not a sizing one. Start with why your AC isn't cooling, then check the air filter and the condenser coils. If the room feels cool but damp, see why your house is so humid.
Frequently Asked Questions
- What size air conditioner do I need for a 12x12 room?
- A 12 by 12 foot room is 144 sq ft, which falls in the ENERGY STAR band for rooms up to 150 sq ft: about 5,000 BTU. Add 10% if the room is very sunny, or 4,000 BTU if it is a kitchen.
- What size air conditioner do I need for a 10x10 room?
- A 10 by 10 foot room is 100 sq ft, which the ENERGY STAR chart puts at about 5,000 BTU. Add 10% if the room is very sunny, 600 BTU for each person beyond two, or 4,000 BTU if it is a kitchen.
- What size air conditioner do I need for a 12x14 room?
- A 12 by 14 foot room is 168 sq ft, which the ENERGY STAR chart puts at about 6,000 BTU. Add 10% if the room is very sunny, 600 BTU for each person beyond two, or 4,000 BTU if it is a kitchen.
- Is a bigger air conditioner better?
- No. An oversized unit cools the air quickly and shuts off before it has pulled moisture out of the room, which leaves it cool but clammy, and the frequent on-off cycling wastes energy. Pick the closest common size at or just above your number.
- How much should I add for a kitchen?
- ENERGY STAR recommends adding 4,000 BTU when the unit will cool a kitchen, to offset heat from cooking appliances.
- Does the number of people in the room matter?
- Yes. The sizing chart assumes two people. If more than two people regularly use the room, add 600 BTU for each extra person.
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