Tiling a floor, shower wall, or backsplash is one of the most rewarding weekend projects you can tackle, but the planning step is where most people stumble. Get the measurements wrong or ignore waste, and you'll be making an extra hardware store run mid-project. This guide walks you through everything you need to know before you buy a single tile.
For a rectangular floor or wall, measuring is simple: multiply the length by the width to get square footage. A 10-foot by 12-foot bathroom floor is 120 square feet. The catch is that most rooms are not perfect rectangles. Measure each section separately and add them together. For a backsplash, measure the full width of the area and the height from counter to cabinet, then subtract any windows or large openings.
Measure the longest length and widest width of the room, even if parts of the floor are covered by cabinets or a vanity. Tile runs under most fixtures, and you want to account for the full field. For an L-shaped bathroom, break it into two rectangles, calculate each, and add them.
Measure each wall panel individually. For a shower surround with three walls, measure each wall's height and width separately. Subtract the area of the showerhead cutout and niche if you have one, though these are small enough that most tilers just leave them in the waste buffer.
Measure the total linear width of your backsplash run and multiply by the height (typically 18 inches from counter to upper cabinet). Subtract the area of any windows, range hoods, or outlets that tile will not cover.
Never buy exactly the square footage you measured. Tile breaks, cuts waste material, and patterns require extra pieces to maintain alignment. As a general rule, add 10 percent for basic grid layouts on rectangular rooms. Bump that to 15 percent for diagonal patterns, which require more cuts at every wall edge. Add up to 20 percent for intricate herringbone or Versailles patterns, very small tiles, or rooms with lots of corners and niches. Tile from different production batches can have slight color variation, so buying extra upfront and storing a few pieces prevents a visible mismatch if you ever need to repair a cracked tile later.
Tile size affects both the look of the room and the amount of work involved. Large-format tiles (18x18 or bigger) make a small room feel more open because there are fewer grout lines. However, they require a very flat subfloor. Any dip or hump over a 10-foot span should be no more than 3/16 of an inch for tiles larger than 15 inches on any side. Small mosaic tiles (2x2 or smaller) are forgiving on curved or uneven surfaces like shower floors, and they provide more grout lines for traction. Medium tiles in the 12x12 to 16x16 range are the workhorse choice: easy to work with, widely available, and appropriate for most residential floors and walls.
A common rule of thumb is to avoid tiles that are more than half the width of the narrowest dimension of the room. In a 4-foot-wide hallway, a 24-inch tile would feel oversized and produce awkward cut slivers at both walls. A 12-inch tile lets you maintain balanced cuts on each side.
A standard grid pattern (tile edges aligned in both directions) is the most efficient layout and wastes the least material. A brick or offset pattern, where each row is shifted half a tile, is nearly as efficient and is very popular for subway tile. Diagonal layouts rotate tiles 45 degrees to the wall and create a dramatic look, but every tile along the perimeter needs to be cut, which significantly increases waste and labor. Herringbone patterns, where rectangular tiles are arranged in a zigzag, are striking but time-consuming and require the highest waste factor. Choose your pattern before you buy materials so you account for the correct waste percentage.
The most common mistake is starting from a wall rather than finding the center of the room. Centering your layout means cut tiles on opposite sides are mirror images of each other, which looks intentional and professional. Starting from a wall almost always results in an awkward thin sliver on the opposite side. Another frequent error is skipping a dry layout, or setting tiles out without adhesive to preview the pattern before committing. Spend 20 minutes dry-fitting your first few rows; it reveals alignment issues before they become permanent. Finally, do not skip the spacers. Consistent grout joints are what separate a professional-looking job from an amateur one, and spacers make it effortless.
Once you know your square footage, estimating grout and mortar is simple. Most thinset mortar bags cover 40 to 50 square feet per 50-pound bag when applied with a standard notched trowel. Grout coverage depends on tile size and joint width. A 1/8-inch grout joint with a 12x12 tile covers roughly 50 square feet per 10-pound bag of sanded grout. Check the manufacturer's coverage chart on the packaging since it varies by product. Always buy one extra bag of each so you are not slowed down mid-project.
