How many 20x20 porcelain floor tiles do you need for 660sf?

You will need 250 tiles.

First, you must calculate how many square feet there are in each tile:

20" X 20" = 400 square inches per tile.

One square foot = 144 square inches (12" X 12" = 144 square inches)

So, 400 square inches per tile divided by 144 square inches per foot = 2.778.

That means there are 2.778 square feet per tile.

Now you can calculate how many tiles you need to cover 660 square feet:

660 square feet divided by 2.778 square feet per tile = 237.58 tiles.

However, in practice, you will also need about 5% for waste (cuts, breakage or defective tiles) - so add that amount:

237.58 X 1.05 = 249.46 tiles.

Round up, and you will need at least 250 tiles.

If you're doing a patterned design or laying tiles on the diagonal, you'll want to increase your waste factor a little bit.

Typically, folks will just round pieces up to the next full box of tiles.