What Size Mini Split Do I Need (BTU by Room Size)?
Reviewed by AC Direct Technical TeamUpdated June 2, 20265 min read
The short answerA mini split needs roughly 20 to 30 BTU per square foot of the room or zone it serves. A 500 sq ft room usually wants a 12,000 BTU (1 ton) unit, and a 1,000 sq ft open space wants about 24,000 BTU. Climate, sun, and ceiling height move the number.
Mini split BTU by room size and climateAC Direct HVAC guide
Size each zone to its own square footage. Use the calculator below.
The quick BTU-per-square-foot guide
Unlike a central system sized in tons for the whole house, a mini split is sized per zone. Each indoor head is matched to the room it serves. The starting figure is 20 to 30 BTU per square foot, higher for sunny or hot spaces.
Room size
Typical BTU
Common unit
150 to 350 sq ft
9,000
0.75 ton
350 to 500 sq ft
12,000
1 ton
500 to 750 sq ft
18,000
1.5 ton
750 to 1,000 sq ft
24,000
2 ton
What moves the number
Sun and climate
A sunny room or a hot climate pushes toward the higher end (30 BTU/sq ft). A shaded room in a mild climate sits at the lower end.
Ceiling height and insulation
High ceilings and weak insulation add load. A vaulted great room needs more than its floor area suggests.
Do not oversize
An oversized mini split short-cycles and leaves humidity behind, just like an oversized central system. Match the head to the room.
Free Tool
Mini Split Sizing Calculator
Estimate the BTU your room needs, then jump to matching mini splits.
About 12,000 BTU
Closest common size: a 12,000 BTU (1 ton) mini split.
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