Mini split BTU chart by room size
Short answer: in an average room, 9,000 BTU covers ~250–350 sq ft, 12,000 BTU ~450–550 sq ft, 18,000 BTU ~600–750 sq ft, 24,000 BTU ~850–1,000 sq ft, 30,000 BTU ~1,100–1,300 sq ft, and 36,000 BTU ~1,350–1,500 sq ft. Hot climate, poor insulation, heavy sun, or tall ceilings shift you up a size. Get an exact figure from the mini split calculator.
The chart
Square footage ranges below assume an average room: 8-foot ceiling, average insulation, moderate climate, and a couple of occupants. Conditions stack — a sunny, poorly insulated garage at the top of a range should move up to the next size.
| BTU size | Sq ft range (average room) | Example rooms |
|---|---|---|
| 9,000 BTU | 250–350 sq ft | Standard bedroom, small home office, nursery |
| 12,000 BTU | 450–550 sq ft | Large bedroom, home office, small studio apartment |
| 18,000 BTU | 600–750 sq ft | Living room, 2-car garage, open studio |
| 24,000 BTU | 850–1,000 sq ft | Great room, large open-plan living/dining |
| 30,000 BTU | 1,100–1,300 sq ft | Open-plan main floor, large workshop |
| 36,000 BTU | 1,350–1,500 sq ft | Very large single open space |
Above 1,500 sq ft, or for several separate rooms, step up to a multi-zone system rather than one oversized head.
By common room type
Bedroom
Most bedrooms are 150–300 sq ft, which is squarely 9,000 BTU territory. A large primary suite over ~350 sq ft, or a bedroom with big west-facing windows, may want 12,000 BTU. Bedrooms are a place where right-sizing pays off: an oversized unit short-cycles, leaving you cold and clammy at night. Run your room →
Home office
A typical home office of 100–250 sq ft sits at 9,000 BTU. Add for electronics heat if you run several monitors and a desktop — those act a little like extra occupants. A converted bedroom-office over ~350 sq ft moves to 12,000 BTU.
2-car garage
A standard 2-car garage is roughly 400–600 sq ft, so the base math points at 12,000–18,000 BTU. But garages are usually poorly insulated, often have an uninsulated door, and can take full afternoon sun — all of which push you to the top of the range. For an uninsulated garage, 18,000 BTU is the safer pick. Set insulation to "poor" in the calculator to see this.
Living room
Living rooms range widely. A modest 350–450 sq ft living room is 12,000 BTU; a larger 600–750 sq ft room or one open to a dining area is 18,000 BTU. Big windows and high ceilings are common here, so don't skip those adjustments.
Open-plan / great room
Open-plan main floors of 850–1,300 sq ft fall in the 24,000–30,000 BTU range for a single head, provided it's genuinely one open space. If walls divide it, you're really sizing multiple zones.
Frequently asked questions
How many square feet does a 12,000 BTU mini split cover?
Roughly 450–550 sq ft in an average room — a large bedroom, home office, or small studio. Less in a hot climate, with poor insulation, or under heavy sun.
How many square feet does a 9,000 BTU mini split cover?
Roughly 250–350 sq ft — a standard bedroom, small office, or nursery.
What BTU mini split for a 2-car garage?
12,000–18,000 BTU, usually toward 18,000 because garages are often uninsulated and sun-exposed.
Related: Mini split BTU calculator · What size mini split do I need? (full guide)