Once you have determined the square footage of the room, by multiplying the length times the width, then you will be able to check the boxes of tile, which will tell you how much square footage one box will cover.
I'm not real good at explaining, but as an example; say you have a room that is 10 feet wide and 13 feet long, it would be 10 times 13, which would equal 130 square feet. Now, if each box of tile covers 15 feet, you would divide 130 by 15, which would be a total of 8.6 boxes of tile. So you will need to purchase nine boxes of tile for that room.
You will probably need the few extra pieces just in case yo
Hope I have explained in a way yo
Good luck to you on your tile job.
I'm not real good at explaining, but as an example; say you have a room that is 10 feet wide and 13 feet long, it would be 10 times 13, which would equal 130 square feet. Now, if each box of tile covers 15 feet, you would divide 130 by 15, which would be a total of 8.6 boxes of tile. So you will need to purchase nine boxes of tile for that room.
You will probably need the few extra pieces just in case yo
Hope I have explained in a way yo
Good luck to you on your tile job.