Tile Calculator

Work out how many tiles and boxes a floor, wall or backsplash needs, counting the space taken by grout joints and extra for cuts and breakage.

1/16 = 0.0625, 1/8 = 0.125, 3/16 = 0.1875, 1/4 = 0.25.

Raise it for diagonal or herringbone layouts and small, cut-up rooms.

Printed on the box or the product page.

Leave at 0 to skip the cost estimate.

Tiles to buy
87
Includes 10% extra
Boxes
9
90 tiles at 10 per box
Area to tile
80 sq ft (7.43 sq m)
Tiles before extra
78.4
Area per tile incl. grout
1.021 sq ft
  • Buy all boxes from the same lot (the code printed on the box): color and size can vary slightly between production runs.
  • Grout, thinset, backer board and trim pieces are not included.

How the tile count works

Each tile covers its own face plus half of the grout joint on every side, so the floor area one tile "uses" is (tile length + joint) × (tile width + joint). Divide the area to be tiled by that, add a percentage for cuts and breakage, and round up. Then divide by the tiles per box and round up again, because tile is sold by the box.

Grout joints matter more for small tiles. On a 12 × 12 inch tile, a 1/8 inch joint adds about 2% to the area each tile covers. On a 2 × 2 inch mosaic, the same joint adds about 13%, which is why mosaic sheets cover noticeably more than the tile faces alone.

How much extra to buy

Every row that meets a wall, cabinet or doorway needs a cut piece, and some cuts are too small to reuse. Some tiles break or turn up chipped. The default 10% is a reasonable starting point for a straight layout in a simple rectangular room. Raise it for diagonal, herringbone or other patterned layouts, for large-format tiles (where a single bad cut costs a lot of area), and for rooms with many corners.

Keep a few spare tiles after the job. Matching a discontinued tile or a different lot years later for a repair can be difficult.

Measuring the area

Measure the floor wall to wall in feet and use decimals for inches (6 inches = 0.5 ft). For an L-shaped room, split it into rectangles, add their areas in the square footage calculator, and enter the total here using "Total area I already know". For a wall or backsplash, measure width × height and subtract windows, but not small outlets or switches.

The formulas

Area per tile = (t_L + g) × (t_W + g) ÷ 144Tiles = round up (A × (1 + waste ÷ 100) ÷ area per tile)Boxes = round up (tiles ÷ tiles per box)
  • A = area to tile in square feet
  • t_L, t_W = tile length and width in inches
  • g = grout joint width in inches
  • 144 = square inches in a square foot

Example: a 10 × 8 ft bathroom floor in 12 × 12 inch tile

  1. Area: 10 × 8 = 80 sq ft.
  2. Area per tile with a 1/8 inch joint: 12.125 × 12.125 ÷ 144 = 1.021 sq ft.
  3. Tiles before extra: 80 ÷ 1.021 = 78.4.
  4. With 10% extra: 80 × 1.10 ÷ 1.021 = 86.2, so buy 87 tiles.
  5. At 10 tiles per box: 87 ÷ 10 = 8.7, so buy 9 boxes (90 tiles).

Frequently asked questions

How many 12x12 tiles do I need for 100 square feet?

Without grout or waste, 100 tiles. With a 1/8 inch joint and 10% extra: 100 × 1.10 ÷ 1.021 = 107.7, so 108 tiles.

How many 12x24 tiles are in a square foot?

A 12 × 24 inch tile covers 2 square feet, so half a tile per square foot. A 100 sq ft floor needs 50 tiles before grout and waste.

Does grout width change how many tiles I need?

Slightly, because the joint takes up floor area. It matters most for small tiles: a 1/8 inch joint adds about 2% to a 12 × 12 tile's coverage but about 13% to a 2 × 2 mosaic.

How much extra tile should I buy?

This calculator starts at 10% for a straight layout. Increase it for diagonal or herringbone patterns, large-format tile and rooms with lots of corners, and keep a few spare tiles for future repairs.

How do I convert tile size in centimeters?

Divide centimeters by 2.54 to get inches. A 30 × 60 cm tile is about 11.81 × 23.62 inches.

Sources

Last reviewed for 2026. How we calculate.