What size window air conditioner do I need?

The first step is to calculate the square footage of your room. Generally, a 5,000BTU air conditioner is suitable for up to 150 sq. ft., 8,000BTUs for up to 300 sq. ft., 10,000 BTUs for up to 500 sq. ft., 12,000 BTUs for up to 700 sq. ft., and 25,000 BTUs for up to 1,500 sq. ft.