What Size Air Conditioner Do I Need for a 250 Sq Ft Room?
250 sq ft closes the 6,000 BTU/hr row and opens the 7,000 BTU/hr row.
Full breakdown: BTU per square foot.
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Capacity from the chart
| Area to be cooled | Capacity needed | Source |
|---|---|---|
| 150 up to 250 sq ft | 6,000 BTU/hr | ENERGY STAR |
| 250 up to 300 sq ft | 7,000 BTU/hr | ENERGY STAR |
The gap between these two capacities is 1,000 BTU/hr. That is 7,000 minus 6,000, and it is bigger than either 10% swing. Ten percent of 6,000 is 600 BTU/hr. Ten percent of 7,000 is 700 BTU/hr. If you only argue about shade and ignore which row 250 sq ft belongs on, you are tuning the smaller number.
How to size it
Read 250 sq ft as the end of one published range and the start of the next. ENERGY STAR writes both as "up to," so the chart itself does not award the square foot to a single row. Use the room, not an average: shaded rooms take the lower capacity, and sunny rooms or rooms with more than two people regularly take the higher one.
| Adjustment | On the 6,000 row | On the 7,000 row | Source |
|---|---|---|---|
| Heavily shaded, reduce capacity 10% | 6,000 − 10% = 5,400 BTU/hr | 7,000 − 10% = 6,300 BTU/hr | ENERGY STAR |
| Very sunny, increase capacity 10% | 6,000 + 10% = 6,600 BTU/hr | 7,000 + 10% = 7,700 BTU/hr | ENERGY STAR |
| Each additional person beyond two | 6,000 + 600 BTU/hr = 6,600 BTU/hr | 7,000 + 600 BTU/hr = 7,600 BTU/hr | ENERGY STAR |
| Unit used in a kitchen | 6,000 + 4,000 BTU/hr = 10,000 BTU/hr | 7,000 + 4,000 BTU/hr = 11,000 BTU/hr | ENERGY STAR |
10% of 6,000 BTU/hr is 600 BTU/hr (6,000 × 10%).
10% of 7,000 BTU/hr is 700 BTU/hr (7,000 × 10%).
Shaded 250 sq ft: start at 6,000 and subtract 10% to reach 5,400 BTU/hr. Sunny 250 sq ft: start at 7,000 and add 10% to reach 7,700 BTU/hr. One person beyond two on the upper row is 7,000 + 600 = 7,600 BTU/hr. A kitchen at this floor area adds 4,000 to the row you already picked, which is 10,000 BTU/hr from the low row or 11,000 BTU/hr from the high row. Do not add the kitchen figure and also jump rows "to be safe" unless the room is both a kitchen and sunny.
Hold the ceiling check until the row is chosen. The capacities assume an 8-foot ceiling. A higher ceiling is ENERGY STAR's cue to select a room air conditioner with a higher CADR, not a license to invent a third row between 6,000 and 7,000.
Where a window opening will not take the unit, compare a ductless head in the mini-split room size guide.
7,000 BTU window air conditioners on Amazon Window air conditioner insulation foam on Amazon
Related questions
- What size air conditioner for a 200 sq ft room
- What size air conditioner for a 300 sq ft room
- What size air conditioner for a kitchen
All of these questions are listed on the topic map.
Sources
- ENERGY STAR, Room Air Conditioners — https://www.energystar.gov/products/room_air_conditioners — accessed Oct 2, 2026.
Frequently asked questions
Is a 250 sq ft room 6,000 or 7,000 BTU/hr?
150 up to 250 sq ft is 6,000 BTU/hr, and 250 up to 300 sq ft is 7,000 BTU/hr. Heavy shade keeps the room on 6,000. A very sunny exposure, or more than two people regularly, is the reason to start at 7,000.
Which matters more here, the row or the 10% adjustment?
The two rows differ by 1,000 BTU/hr (7,000 − 6,000). Ten percent of 6,000 is only 600 BTU/hr, and ten percent of 7,000 is 700 BTU/hr. The boundary choice is larger than the shade tweak, so pick the row before you apply 10%.
What does a kitchen adder do at 250 sq ft?
Add 4,000 BTU/hr after the row is chosen. From 6,000 that is 10,000 BTU/hr. From 7,000 that is 11,000 BTU/hr. People are separate: one person beyond two adds 600 BTU/hr on top of whichever row you picked.
Does a higher ceiling change the 250 sq ft row?
The chart is built on an 8-foot ceiling. ENERGY STAR does not give a new sq ft cutoff for a taller room. It says you may want a room air conditioner with a higher CADR. A central system is outside this chart; use the HVAC load calculator.