Mini Split Calculator
Calculate the correct BTU size for your ductless mini split system based on room dimensions, insulation, climate, and other factors.
Recommended BTU Size
Recommended Unit Size
Room Summary
Climate Zone Reference
- Zone 1-2 (Mild): Florida, Texas, Southern California - Focus on cooling
- Zone 3-4 (Moderate): Mid-Atlantic, Midwest, Pacific NW - Balance needed
- Zone 5-6 (Cold): New England, Great Lakes - Heating priority
- Zone 7-8 (Extreme): Minnesota, North Dakota, Alaska - High heating capacity
BTU Sizing Guide
- 9,000 BTU: Up to 350 sq ft
- 12,000 BTU: 350-550 sq ft
- 15,000 BTU: 550-750 sq ft
- 18,000 BTU: 750-1,000 sq ft
- 24,000 BTU: 1,000-1,500 sq ft
- 30,000+ BTU: 1,500+ sq ft
Sizing Tips
- When in doubt, size up slightly
- Multiple heads? Divide total BTU
- Consider high ceilings (+10-20%)
- Poor insulation = add 20-30%
- Very sunny rooms = add 10-15%
Frequently Asked Questions
How do I size a mini split for my room?
To size a mini split, calculate the room's square footage (length × width), then multiply by 25 BTU per square foot for standard conditions. Adjust for ceiling height, insulation, sun exposure, windows, and number of occupants. Our calculator handles all these factors automatically.
How many BTU do I need per square foot?
The general rule is 20-30 BTU per square foot. Standard rooms need about 25 BTU/sq ft. Adjustments: Poor insulation (+10-20%), high ceilings (+10-20%), sunny rooms (+10-15%), kitchen (+4,000 BTU). Use our calculator for precise sizing.
What size mini split for a 20x20 room?
A 20x20 room is 400 sq ft. Using our calculator: 400 × 25 = 10,000 BTU. The closest standard size is 9,000 or 12,000 BTU. For a standard room with good insulation, 9,000 BTU works. For a sunny room or kitchen, choose 12,000 BTU.
Can a mini split be too big for a room?
Yes! An oversized mini split will short-cycle (turn on/off frequently), leading to:
- Poor humidity control (cooling too fast)
- Higher energy bills
- Uneven temperatures
- Reduced equipment lifespan
What's better for a garage - 9,000 or 12,000 BTU?
For a standard 2-car garage (400-500 sq ft), 12,000 BTU is usually better. Garages typically have poor insulation and larger temperature swings. Our calculator will factor in room type "Garage" to recommend appropriate sizing.
How many mini split heads do I need?
One head per room or zone. For open floor plans, one larger head may suffice. Our calculator recommends total BTU; divide by standard head sizes (6,000, 9,000, 12,000, 15,000, 18,000, 24,000 BTU) to determine number of heads.