Cooling · Ductless
Mini Split Sizing
A bedroom typically takes a 9,000–12,000 BTU mini split; a living room 18,000–24,000 BTU. The right answer depends on climate more than anything else — calculate your room's load, then match it to a standard unit size below.
Room dimensions
- Tons
- 2.45 t
- Kilowatts
- 8.64 kW
- Horsepower
- 3.68 HP
- Room area
- 19.32 m²
- Room volume
- 58.9 m³
Cooling capacity
29,450BTU/h
≈ 2.45 tons · 8.64 kW
Mini split sizes and coverage
Two honest columns: retail-style guidance for mild climates (~25 BTU/sq ft) and this site's hot-climate volumetric method (500 BTU/h per m³). Pick the column that matches your summers.
| Unit (BTU/h) | kW | Mild climate covers | Hot climate covers |
|---|---|---|---|
| 6,000 | 1.8 | 240 sq ft / 22 m² | 53 sq ft / 5 m² |
| 9,000 | 2.6 | 360 sq ft / 33 m² | 79 sq ft / 7 m² |
| 12,000 | 3.5 | 480 sq ft / 45 m² | 106 sq ft / 10 m² |
| 18,000 | 5.3 | 720 sq ft / 67 m² | 159 sq ft / 15 m² |
| 24,000 | 7 | 960 sq ft / 89 m² | 212 sq ft / 20 m² |
| 30,000 | 8.8 | 1,200 sq ft / 111 m² | 265 sq ft / 25 m² |
| 36,000 | 10.6 | 1,440 sq ft / 134 m² | 318 sq ft / 30 m² |
The gap between the columns is real: mild-climate guidance assumes moderate design temperatures, insulation, and 8-ft ceilings, while hot-climate sizing must survive peak sun and heat waves. When in doubt, run the calculator with your dimensions and round up to the next unit size in hot climates.
Multi-zone systems
Size each indoor head to its own room using the calculator, then choose the outdoor unit near the sum of the heads. Outdoor units typically allow up to 130% combined indoor capacity because rooms rarely peak together — but if every zone bakes at the same hour (west-facing bedrooms, one-story homes), keep the total at or below 100%. Estimate the whole house room-by-room with the HVAC load calculator.
FAQ
- What size mini split do I need for a bedroom?
- A standard bedroom takes a 9,000 BTU unit in a mild climate. In a hot climate, or with large west-facing windows, step up to 12,000 BTU — run the calculator above with your exact dimensions to check which side of the line you are on.
- Why do coverage charts disagree so much?
- Retail charts assume a mild climate: about 25 BTU per square foot with 8-foot ceilings and decent insulation. Hot-climate sizing methods, like the volumetric formula this site uses, allow several times more capacity per square foot to survive 100 °F+ peaks, high solar gain, and lighter construction. Neither is wrong — they answer different climates, which is why the chart below shows both.
- Can a mini split be too big?
- Yes, but the penalty is smaller than with fixed-speed ACs: inverter compressors modulate down to roughly 30–40% of rated capacity. Below that floor an oversized unit still short-cycles and dehumidifies poorly, so stay within one size step of the calculated load.
- How do I size a multi-zone mini split?
- Size each indoor head to its own room's load, then pick an outdoor unit rated near the sum. Because rooms rarely peak at the same time, outdoor units support a combined indoor rating of up to 130% of their capacity — but keep the total near 100% if all rooms run hot simultaneously.
- Do mini splits heat as well as cool?
- Most are heat pumps and heat efficiently to around −15 °C (5 °F); cold-climate models work below −25 °C. Heating capacity at low temperature is the number to check — it is usually lower than the rated cooling capacity.