How much space should I leave when grouting ceramic tile?

When you are grouting ceramic tile, you will only have the amount of space that corresponds to the size of the tile spacer that you used. You could potentially use a 1/4" grout line or even a 1/8" grout line. When you fill up the grout line with grout, you need to make sure that you do not fill it all the way to the top. Leave about 1/8" to 1/4" of room on top of the grout to the top of the tile that is next to it. This way, you will not walk directly on the grout when you walk on the floor.