Load intensity: — BTU/hr per sq ft | — tons
Recommendation Summary
| Recommended size | — |
| Acceptable range | — |
| Calculated load | — |
| Room load level | — |
| Mode | — |
Mini Split Sizing Chart
| Room size | Typical mini split |
|---|---|
| 150 – 250 sq ft | 6,000 BTU |
| 250 – 450 sq ft | 9,000 – 12,000 BTU |
| 450 – 750 sq ft | 12,000 – 18,000 BTU |
| 750 – 1,000 sq ft | 18,000 – 24,000 BTU |
| 1,000 – 1,300 sq ft | 24,000 – 30,000 BTU |
Adjust up for poor insulation, high sun, tall ceilings, or hot climates; down for tight, shaded, well-insulated rooms.
What Size Mini Split Do I Need?
Mini splits are sold in fixed sizes, so the real question is which size to buy. This calculator turns your room into a recommended unit, not just a BTU number. Enter the room size, ceiling height, insulation, climate, and sun exposure, choose cooling or heating, and it returns the mini split size to buy, an acceptable range, and whether your room is a light, medium, or heavy load. Mini splits run roughly 25 to 30 BTU per square foot, more than a ducted central system, because each head conditions one space directly.
Mini Split Too Big vs Too Small
Oversizing is the more common mistake. An oversized mini split cools the air quickly, then shuts off before it can pull humidity out, so the room feels clammy and the compressor short-cycles, wearing out faster and wasting energy. An undersized unit runs constantly and still cannot keep up on the hottest or coldest days. The sweet spot is matching the unit to the calculated load, which is why this tool gives an acceptable range and warns when rounding up would oversize the room.
Single-Zone vs Multi-Zone
A single-zone system is one indoor head paired with one outdoor condenser, the simplest and most efficient option for one room. A multi-zone system runs two or more heads off a single condenser, handy when you want to condition several rooms without multiple outdoor units. Multi-zone condensers are sized to the combined load with a small diversity allowance, since not every room peaks at once. Switch the zones selector above to size a multi-zone system head by head.
Garage Mini Split Sizing Example
Garages are tricky: they are often poorly insulated, have a big uninsulated door, and pick up heat from a south-facing wall. A 500-square-foot garage with poor insulation in a hot climate can need 14,000 to 18,000 BTU, well above what the square footage alone suggests. Select the garage room type and poor insulation above to see the adjusted size. Insulating the garage door first can drop you a full unit size.
Basement Mini Split Sizing Example
Basements are the opposite of garages. Being below grade, they stay cool and stable, so they usually need less cooling than their square footage implies, often a 9,000 to 12,000 BTU unit for a 500 to 700 square foot finished basement. Heating can be the bigger need if the space is used in winter. Pick the basement room type to apply the lower load factor.