AC Tonnage Calculator: Insert Sq Ft, Get Tons (+ Chart)
Upstairs: 1810 sq ft × 30 BTU per sq ft = 54,300 BTU = 4.5 ton AC unit. Downstairs: We can be a bit more conservative here and presume 25 BTU per sq ft. 2569 sq ft × 25 BTU per sq ft = 64,225 BTU = 5.35 ton AC unit. You can see that the downstairs would require a bigger unit since you have 700+ sq ft there compared to the upstairs.