Question

How many 18" square tiles are needed to pave the door of a patio that measures
18 by 15

Answer 1

assuming you want to cover 18 ft x 15 ft:

18 x 15 = 270 ft²

1.5 x 1.5 = 2.25 ft² per tile

270 ft²/ 2.25 per tile = 120 tiles