What size air conditioner for 200 square feet?
Around 7,000 BTU, with caveats that can move the number.
A 200 sq ft room with an 8 ft ceiling needs roughly 6,000 to 8,000 BTU/h. The right commercial unit is usually a 6,000 or 8,000 BTU model, not a 12,000.
The calculation, step by step
For a 200 sq ft room with an 8 ft ceiling, average insulation, two people and 20 sq ft of west-facing glazing with blinds:
Swipe to see the whole table
| Item | Watts | Where it comes from |
|---|---|---|
| Envelope and ventilation | 1,858 | 46.5 m³ x 40 W/m³ |
| Occupants | 240 | 2 people x 120 W |
| Solar gain | 195 | 1.86 m² x 150 W/m² x 0.7 (blinds) |
| Subtotal | 2,293 | |
| 10 % margin | 229 | |
| Total | 2,522 W | = 8,607 BTU/h = 0.72 tons |
How it shifts with your situation
Swipe to see the whole table
| Scenario | BTU/h | Unit |
|---|---|---|
| Well insulated, north facing, no direct sun | 6,300 | 6,000 BTU |
| Standard (the example above) | 8,600 | 8,000-9,000 BTU |
| Large unshaded west window | 9,600 | 9,000-10,000 BTU |
| Top floor, poor insulation, hot climate | 12,300 | 12,000 BTU |
Why two 200 sq ft rooms do not ask for the same unit
The table above shows it without saying it: there is nearly twice the capacity between the best case and the worst, and both rooms measure exactly the same. Floor area is where everyone starts because it is the one number everyone knows, but it is also the weakest input of the lot.
At this size what usually decides is the envelope, meaning where the heat gets in:
- A top floor is a different problem. Under the roof, heat comes in through the ceiling all day, and that surface is as large as the floor.
- One unshaded west-facing window can add more heat on its own than the people and appliances put together, and it does it during the three worst hours.
- Ceiling height multiplies the volume. The same 200 sq ft at 10 ft is 23 % more air to cool than at 8 ft.
Which is why this guide gives a range rather than a figure: anyone selling you a unit on floor area alone has not asked what they needed to ask.
If the room is a bedroom
A 200 sq ft bedroom usually needs less than a living room of the same size: fewer people, fewer appliances running, and it is used at night when there is no direct solar gain. A 6,000 BTU unit is often plenty, and it will run more continuously and quietly.
What it will cost to run
An 8,000 BTU unit of average efficiency draws about 700-800 W. At 8 hours a day and $0.17/kWh, that is roughly $1 a day, around $30 a month of heavy summer use.
Sources and methodology
Conversions use exact constants: 1 BTU/h = 0.29307107 W and 1 frigorie/h = 1 kcal/h = 1.163 W. The component sizing model (load per volume by insulation level, 120 W per person, solar gain by glazed area) is set out in full on the air conditioner size calculator. It is a guideline estimate: a professional heat-load calculation considers considerably more variables.
Frequently asked questions
How many BTU do I need for a 200 sq ft room?
Between 6,000 and 8,000 BTU/h under normal conditions. With poor orientation or insulation it can rise to 10,000-12,000.
Is a 12,000 BTU unit too big for 200 square feet?
Usually yes, unless it is a top-floor room with heavy sun or poor insulation. An oversized unit short-cycles and dehumidifies badly.
What size AC for a 200 sq ft bedroom?
6,000 BTU is typically enough: fewer occupants, fewer appliances and night-time use with no solar gain.
How much does it cost to run?
An 8,000 BTU unit draws roughly 700-800 W, so about $0.13 per hour at $0.17/kWh, or around $30 a month at 8 hours a day.
Does the same unit suit a living room and a bedroom?
Not necessarily. A 200 sq ft living room usually has more occupants, more appliances and more sun than a bedroom of the same size.