HVAC & BTU Calculators

BTU sizing for air conditioners and mini-splits — find the cooling capacity a room needs and the right unit size.

CalcBooth’s HVAC calculators size cooling to a room. The BTU calculator works out how many BTUs an air conditioner needs from the room area, ceiling height, sun exposure, climate and how the space is used, then suggests a standard unit size. The mini-split sizing calculator does the same and points you to the nearest 9k, 12k, 18k or 24k BTU mini-split. The BTU converter explains what a BTU is and converts between BTU/hr, kilowatts, watts and tons of cooling. These are quick rule-of-thumb estimates to get you in the right range; a contractor’s Manual J load calculation is the precise sizing for a permanent install.