How to measure for tile
For a floor, measure the length and width of the room in feet. For a wall or backsplash, measure its length and its height. If the area is not a rectangle, split it into rectangles, run the calculator for each one and add the tiles together.
Enter the tile size printed on the box. Tile is often sold with a nominal size, so a "12 × 24" tile may actually measure a little less. Using the nominal size gives you a slightly higher count, which is the safe direction.
How the calculation works
Area (sq in) = length × width × 144
Space per tile (sq in) = (tile length + joint) × (tile width + joint)
Tiles = area ÷ space per tile × (1 + waste %), rounded up
Boxes = tiles × tile area ÷ coverage per box, rounded up
In the example above, an 8 × 10 ft floor is 80 square feet, or 11,520 square inches. A 12 × 12 inch tile with a 1/8 inch grout joint takes up 147 square inches, so the floor needs 78.4 tiles before waste. Adding 10% brings it to 87 tiles. Boxes that cover 15 square feet hold 15 of these tiles, so you need 6 boxes.
How much extra tile should you buy?
Tiles get cut at every wall, around doors and pipes, and the occasional tile cracks or arrives chipped. Extra tile also gives you spares for future repairs, which matters because a discontinued tile can be impossible to match later.
- 10% for a straight layout in a simple room.
- 15% for diagonal, herringbone and other patterns where more tiles are cut at an angle.
- 20% for complicated patterns, rooms with many corners, or large tiles where a single bad cut wastes a lot of material.
Choosing a grout joint
Rectified tiles, which have precisely cut edges, are often installed with joints as narrow as 1/16 inch. Most other floor tiles use 1/8 to 1/4 inch joints to make up for small differences in size. The tile manufacturer usually recommends a minimum joint width, so check the box or the product page before you buy spacers.
Tips before you buy
- Buy all your tile at once and check that every box has the same shade or lot number.
- Open a few boxes and lay tiles side by side before you start. Natural variation is normal, but mixing tiles from several boxes as you go gives a more even look.
- Thinset and grout coverage depends on the trowel size and joint width. The bags list how much area they cover, so buy those once you know your tile size.
Frequently asked questions
How many 12 × 12 tiles do I need for 100 square feet?
About 108 tiles with 1/8 inch grout joints and 10% extra. Without counting the grout joints you would plan on 110, so the joints save you only a couple of tiles at this size.
Does the grout joint change how many tiles I need?
Slightly. Each joint takes up a little of the area that would otherwise be tile. The effect is bigger for small tiles: with mosaic or 2 × 2 inch tiles, the joints can account for 10% of the area or more.
How do I calculate tile for a shower?
Calculate each wall separately, using its width and the height you plan to tile, and add the results. Subtract the area of large openings such as a window, and calculate the shower floor on its own, since it often uses a different, smaller tile.
Should I buy extra tile for later repairs?
Yes. Keeping a few spare tiles, or a full box for a large floor, means you can replace a cracked tile years later with an exact match.
This calculator gives an estimate for buying materials. Your installer may suggest a different waste allowance for your layout and tile.