MINI-SPLIT
MINI-SPLIT SIZE
BTU/hr = ft² × climate_factor
ft²
RESULT
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FILL IN ABOVE
Sized per indoor head. Standard sizes: 9k, 12k, 18k, 24k, 36k BTU/hr. Multi-zone systems share an outdoor unit but each indoor head is sized to its room.
About this calculator
This mini-split sizing calculator returns the cooling and heating capacity needed per indoor head for a ductless system. Mini-splits are sized per zone (one indoor head per room or open area), and standard residential head sizes are 9,000, 12,000, 18,000, 24,000, and 36,000 BTU/hr. The cooling load runs about 25 BTU/ft² for a single zone (slightly higher than central AC because zones do not share air handling), and heating load matches the climate-zone rule used for furnaces. For open-concept spaces over 600 ft², a single high-capacity head is usually less efficient than two smaller heads on a multi-zone system.