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.
Mini Split Sizing Calculator
Estimate the BTU your room needs, then jump to matching mini splits.
Estimate only. Ceiling height, insulation, and windows move the number.
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Common mini split sizing questions
What size mini split for a 500 sq ft room?
How many BTU per square foot for a mini split?
Can a mini split be too big?
Do I size each zone separately?
25 years sizing and shipping HVAC systems to homeowners and contractors.
