Guide
How many square feet a mini split cools
Every common size, in a hot, a mixed and a cold climate.
Short answer
A 12,000 BTU (1 ton) mini split cools about 520 sq ft of an average house in a mixed climate, around 430 sq ft in a hot one and 620 sq ft in a cold one, with 8 ft ceilings. That area has to be one open space: a mini split head cannot cool the room next door.
Square feet covered, by size and climate
| Mini split | Zone 2, hot | Zone 4, mixed | Zone 6, cold |
|---|---|---|---|
| 6,000 BTU (0.5 ton) | 210 sq ft | 260 sq ft | 310 sq ft |
| 9,000 BTU (0.75 ton) | 320 sq ft | 390 sq ft | 460 sq ft |
| 12,000 BTU (1 ton) | 430 sq ft | 520 sq ft | 620 sq ft |
| 15,000 BTU (1.25 ton) | 530 sq ft | 650 sq ft | 770 sq ft |
| 18,000 BTU (1.5 ton) | 640 sq ft | 780 sq ft | 920 sq ft |
| 24,000 BTU (2 ton) | 850 sq ft | 1,040 sq ft | 1,230 sq ft |
| 30,000 BTU (2.5 ton) | 1,070 sq ft | 1,300 sq ft | 1,540 sq ft |
| 36,000 BTU (3 ton) | 1,280 sq ft | 1,560 sq ft | 1,850 sq ft |
A room with a kitchen, a lot of west-facing glass, high ceilings or more than two people in it regularly needs a larger unit than the table shows; the mini split calculator adds each of those.
In a cold climate, heating decides the size
A mini split is usually a heat pump, and in climate zones 5 and colder the heating load per square foot is roughly twice the cooling load. A unit sized for summer will be short in winter. Size on the heating load there, and check the unit’s heating capacity at your winter design temperature, not its nominal rating, which is measured at a mild 47°F.
Why bigger is not safer
An oversized mini split cools the room fast and shuts off before it has removed the humidity, so the room ends up cold and clammy. Inverter units modulate down a long way, which softens the problem, but the correct size is still the smallest one that covers the load. More on that in why oversizing is worse.