How much tiles is reqd for 1800 sft area for 1818 tiles?

First, find the square footage of an 18" x 18" tile. 18 x 18 = 324 square inches. There are 144 square inches in a square foot (12" x 12" = 144). So divide 324 by 144 to get the square feet per tile. 324 / 144 = 2.25 sq ft per tile.

You have 1800 square feet, using tiles that are 2.25 sq ft each. 1800 / 2.25 = 800 tiles.

Generally, you will want to add from 5% to 10% for waste, depending on your layout (is it one big room, or several smaller rooms with lots of cutting?) (are you doing a checkerboard pattern, running bond (brick), or diagonal?) and your skill level. If in doubt, add 10% to be safe.

800 tiles + 10% --- that's 800 x 1.1 = 880 tiles.