Using tile spacers that measure 1/8 inch gives the gaps between the tiles in your bathroom a neat, uniform look. This size of spacer is ideal whether you use small or large tiles around your bathroom tub. Other common sizes of spacers include 1/4 inch and 1/16 inch. Typically, use the 1/4-inch size for large tiles, such as at the front entrance of a home, and the 1/6-inch size for small tiles, such as those in a kitchen backsplash.
Spacers are typically small, X-shaped pieces of plastic that measure roughly one half-inch in length. It's possible to get different sizes of spacers at home improvement stores, but the "X" style of spacer is common. They are often sold in bags of 100 or more, so you can leave one in place between each tile throughout the duration of the job.
Using spacers for any tile job is a simple process. After you have laid the backer board and covered it in a layer of thin-set mortar, place one tile into the thin set in the desired location. Set one or more tile spacers firmly against the edge of the tile and push another tile against the spacers. When everything is snug, the spacers ensure a consistent gap between the tiles. Remove the spacers only when you've laid all the tile and are ready to apply the grout.
Although using spacers is the best way to help you maintain a consistent gap between the tiles, many experienced contractors can lay tile without spacers. If you have worked with tile several times in the past and have the eye for it, it's possible to lay tile effectively without spacers. The benefit to this process is it's often quicker, because inserting and removing all the spacers requires significant time.