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Mini Split Size Calculator

A starting estimate for one room. Size for the load, then check the heating numbers.

HomeClimateScout Editors Updated How we rate →
Choose your climate zone. ZIP lookup is not available.

Default: 450 sq ft, sunny, 8 ft ceiling, average insulation, zone 5.

Rule-of-thumb estimate

About 10,900 BTU/h

Look at a 12k head, then get the load checked.

Planning range: 9,300– 12,500 BTU/h.

Cold-climate flag: check heating output at 5°F in the NEEP directory. Nominal BTU is not winter heating output.

A rule of thumb, not a Manual J load calculation. Call a pro for a whole home, multiple zones, poor insulation, or a very cold climate.

Understand mini split ratings →

Mini split size chart

Average insulation, 8 ft ceiling, average sun, two occupants. Editorial estimate: 22 BTU/h per sq ft.
Area · sq ft Estimate · BTU/h Next standard head
400 8,800 9k
500 11,000 12k
600 13,200 18k
800 17,600 18k
1000 22,000 24k
1200 26,400 36k

How we estimate

Area × 22 × ceiling height ÷ 8. Multiply by 1.2 for poor insulation or 0.9 for good insulation; by 1.1 for sunny exposure or 0.9 for shade. Add 600 BTU/h per person above two, 4,000 for a kitchen or 2,000 for a garage. The displayed planning range is ±15%. These are our screening assumptions, not a published load-calculation standard.

Climate zone triggers the cold-climate warning; it does not replace a heating-load calculation. Room separation and air distribution may require more than one head.

Compare SEER2, HSPF2 and cold-weather capacity →

Sources & checks

View all 2 source records and check dates