Mini Split Sizing Guide: BTU by Room Size
Quick Answer: For a single room: match BTU to room size (e.g., 12,000 BTU for 400–600 sq ft). For whole house: calculate total cooling load and consider multi-zone ...
Mini Split BTU by Room Size
| Room Size | Mini Split BTU | Tonnage | Typical Room |
|---|---|---|---|
| 150–250 sq ft | 6,000 | 0.5 ton | Bedroom, office |
| 250–400 sq ft | 9,000 | 0.75 ton | Master bedroom |
| 400–600 sq ft | 12,000 | 1 ton | Living room |
| 600–800 sq ft | 15,000–18,000 | 1.25–1.5 ton | Large living area |
| 800–1,200 sq ft | 24,000 | 2 ton | Open-plan apartment |
| 1,200–1,600 sq ft | 30,000–36,000 | 2.5–3 ton | Small house floor |
Single-Zone vs Multi-Zone
| Feature | Single-Zone | Multi-Zone |
|---|---|---|
| Indoor Units | 1 | 2–5 |
| Best For | One room, addition | Whole house, multiple rooms |
| Cost | $1,500–3,500 | $3,000–8,000 |
| SEER Range | 16–33 | 16–22 |
| Installation | 1 day | 1–2 days |
Common Mistakes
- Oversizing "just in case": Leads to short-cycling, poor humidity control, and higher bills
- Ignoring insulation upgrades: If you've improved insulation, you may need a smaller unit
- Not considering duct condition: Leaky ducts can reduce effective capacity by 20–30%
Frequently Asked Questions
What size mini split do I need?
For a single room: match BTU to room size (e.g., 12,000 BTU for 400–600 sq ft). For whole house: calculate total cooling load and consider multi-zone systems with 2–4 indoor units.
How many BTU mini split per square foot?
Use 20–25 BTU/sq ft in moderate climates, 25–30 in hot climates. A 400 sq ft room needs 9,000–12,000 BTU mini split.
Can one mini split cool a whole house?
A single-zone mini split can cool an open-plan area up to ~1,500 sq ft. For multiple rooms, use a multi-zone system with 2–4 indoor units connected to one outdoor unit.
Are mini splits more efficient than central AC?
Yes. Mini splits typically have SEER 16–33 vs central AC's 14–21. They also avoid duct losses (which account for 20–30% of energy loss in ducted systems).
Disclaimer: Sizing estimates are preliminary. Final equipment selection should use ACCA Manual J load calculation by a licensed HVAC contractor.