A mini split air conditioner calculator sizes ductless AC by room — not whole home. Each indoor head serves one zone, so you calculate BTU per room and buy the matching head capacity. Multi-zone systems sum independent zone loads.
Mini Split BTU by Room Size
| Room sq ft | Recommended BTU | Common head size |
|---|---|---|
| 100 – 200 | 6,000 – 9,000 | 6k or 9k |
| 200 – 350 | 9,000 – 12,000 | 9k or 12k |
| 350 – 500 | 12,000 – 18,000 | 12k or 18k |
| 500 – 700 | 18,000 – 24,000 | 18k or 24k |
| 700 – 1,000 | 24,000 – 30,000 | 24k or 30k |
Apply climate adjustments: +10–15% in hot/humid zones, −10% in cool zones. Add 10% for 9-ft ceilings, 25% for 10-ft ceilings.
Mini Split BTU by Room Size
How a Mini Split Air Conditioner Calculator Works
BTU = Sq ft × 20 × Ceiling Factor × Climate Factor
Unlike central AC, there are no duct losses to account for — ductless systems deliver air directly from the wall head. That efficiency advantage is one reason mini-splits often outperform central AC in additions, garages, and single-room cooling.
Multi-Zone Sizing
| Layout | Approach |
|---|---|
| Open plan (kitchen + living) | One large head or two smaller heads |
| Bedrooms | One head per bedroom |
| Whole home (4+ rooms) | Multi-zone outdoor unit with 2–5 heads |
Do not size one head for an entire 2,000 sq ft home unless it is genuinely open plan. Closed doors block airflow between zones.
Multi-Zone Layout: One Head Per Zone
Mini Split vs Central Air
See Mini-Split vs Central Air for the full comparison. Mini-splits win on additions, zone control, and homes without ducts. Central air wins on whole-home distribution and lower per-BTU cost at large scale.
Use the Free Calculators
Mini-Split Calculator — mini split air conditioner calculator with climate and ceiling adjustments.
HVAC BTU Calculator — room BTU for any AC type.
What Size Mini Split Do I Need? — detailed sizing guide.
FAQ
How many BTU mini split for a 400 sq ft room?
Roughly 9,000–12,000 BTU in a moderate climate. Hot climates or high ceilings push toward 12,000–14,000 BTU.
Can one mini split cool a whole house?
Only if the floor plan is genuinely open. Most homes need 2–5 heads on a multi-zone outdoor unit.
Is a mini split air conditioner calculator accurate?
Within ±15% for single rooms with standard construction. Sun-heavy rooms and poor insulation need manual upward adjustment.