Mini-Split Sizing Calculator
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Mini-split size by room
Mini-split indoor heads come in standard BTU sizes. The calculator above gives a climate-adjusted recommendation, but here is a quick reference for a moderate climate with average insulation:
| Room size | Typical head size |
|---|---|
| 100–250 sq ft | 9,000 BTU (0.75 ton) |
| 250–400 sq ft | 12,000 BTU (1 ton) |
| 400–600 sq ft | 18,000 BTU (1.5 ton) |
| 600–900 sq ft | 24,000 BTU (2 ton) |
| 900–1,200 sq ft | 30,000–36,000 BTU (2.5–3 ton) |
Hot, sunny climates push these up; mild or well-shaded rooms push them down. The calculator above adjusts for your state’s climate zone and sun exposure. For multi-room coverage, size each room independently and match the total to a multi-zone outdoor condenser — most residential condensers support 2 to 5 indoor heads.
Mini-split vs central AC cost
A single-zone mini-split is often cheaper than a central system, but multi-zone installations add up quickly. For a 3 to 4 zone whole-home mini-split setup, the total installed cost often approaches or exceeds a ducted central heat pump, especially if the home already has ductwork. Compare both options for your state with the whole-home vs mini-split calculator.
What size mini-split do I need?
Enter a room’s square footage and your state, and this tool recommends a mini-split head size in BTU, adjusted for climate and sun exposure. For several rooms, size each zone and match a multi-zone condenser.
Frequently asked questions
What size mini-split for a 400 sq ft room?
Around 12,000 to 18,000 BTU depending on climate and sun exposure; the calculator recommends a specific head size for your room and state.
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