The difficulty in calculating square footage is correctly measuring your area. I am going to post a picture below and give you the area (width/height) under the left of the cabinets, the under to the right of the cabinets and then the center area. Once we have those measurements I am going to explain how to calculate the math so you know that you are buying enough but not too much tile.
From the left side to center is: 14"t x 22"w
From the right side to center is: 14"t x 23"w
Center area is: 38"t x 32"w
What you do next is multiply each section width x height and that will give you the total number of square inches
Area 1: 14 x 22 = 308
Area 2: 14 x 23 = 322
Area 3: 38 x 32 = 1216
TOTAL 1846 square inches
Now you take that number and you divide it by 144 which is the number of sq inches in 1 sq ft
1846 / 144 = 12.819 sf
So now you know that you have 13 sf (you have to round up no matter what is after the decimal.
Now the general rule of thumb in construction is to add 10% to the total number of sq ft needed, so in this case: