Porcelain floor tile is one of the more delicate types, and when you try to cut it with tile cutters it keeps chipping and cracking. The trick to cutting porcelain floor tile is a wet saw, available at a tool rental centre (or you can buy one; they're relatively inexpensive).
Mark your cutting lines on each porcelain tile, using a china marker and double checking your measurements before marking. For corner cutouts, mark both sides of the tile.
Fill the water reservoir on the wet saw to the "Fill" line and plug it in.
Turn on the wet saw and make sure the water is circulating.
Place the tile on the guide plate with the edge facing your body flat against the plate and the cutting line facing straight into the saw blade.
Push the tile into the saw blade at the cutting mark, using one hand on the guide to push and your other hand to hold the tile in place. Push with a slow, steady motion and don't push the tile into the blade too fast; let the saw do the work.
Cut the waste piece of tile to the end. You'll have a smooth, clean cut with no chipping. For a corner cutout, cut only to the end of the cutting line.
Flip the tile over and cut the second line in the same manner if you're making a corner cutout.
Always use eye protection when cutting porcelain tile. When operating a wet saw: do so outside if possible, because it's a messy job with a lot of spray. Never operate the saw near children or pets, or leave it unattended near them. Be extremely careful as your hands near the blade in the cutting process.