What size room will a 12000 btu heat pump and cool?

A 12,000 BTU heat pump can cool a room approximately 1,000 square feet or heat a room approximately 800 square feet. Please note that the actual size of the room that a heat pump can heat or cool efficiently may vary based on various factors, such as insulation levels, climate conditions, and ductwork design. It is always best to consult with an HVAC professional to determine the appropriate size heat pump for your specific needs and room size.