Tile count formula with waste factors: add 10% for straight layouts, 15% for diagonal, 20% for herringbone. How tile size changes the total.
Tile is sold by the piece, by the box, or by the square foot, and size drives the count directly. The most common floor tile sizes are 12 by 12 inches (1 square foot each), 18 by 18 inches (2.25 square feet), and 24 by 24 inches (4 square feet). Wall tiles are often smaller, with 4 by 4 inch, 6 by 6 inch, and 3 by 6 inch subway tiles being standard. Mosaic tiles usually come mounted on 12 by 12 inch mesh sheets.
Larger tiles mean fewer pieces but more cutting waste at the edges, while smaller tiles mean more pieces but easier fitting around obstacles. A 12 by 12 foot room takes 144 of the 12 by 12 inch tiles but only 36 of the 24 by 24 inch tiles before accounting for waste. The choice of size therefore changes both the labor and the waste budget.
Manufacturers package tiles by the box, and the square footage per box varies by product. A typical box of 12 by 12 inch ceramic tile holds 10 to 20 square feet, so a 100 square foot project may need anywhere from 5 to 10 boxes. Always check the box label for exact coverage, because two boxes that look identical can contain different numbers of tiles.
The formula converts the room area and the tile size to the same units, then divides. For tiles measured in inches, convert to square feet by dividing the tile area in square inches by 144 (the number of square inches in a square foot).
Number of tiles = Floor area (sq ft) ÷ Tile area (sq ft)
Worked example: a 10 by 12 foot bathroom floor is 120 square feet. Using 12 by 12 inch tiles (1 square foot each) gives 120 tiles. Using 18 by 18 inch tiles: each tile is 18 × 18 = 324 square inches, or 324 ÷ 144 = 2.25 square feet, so 120 ÷ 2.25 = 53.3, rounded up to 54 tiles. Using 24 by 24 inch tiles (4 square feet each): 120 ÷ 4 = 30 tiles.
| Tile Size | Area per tile — tiles per 100 sq ft (before waste) |
|---|---|
| 12 × 12 in | 1.00 sq ft — 100 tiles |
| 16 × 16 in | 1.78 sq ft — 57 tiles |
| 18 × 18 in | 2.25 sq ft — 45 tiles |
| 24 × 24 in | 4.00 sq ft — 25 tiles |
| 12 × 24 in (plank) | 2.00 sq ft — 50 tiles |
No tile job uses exactly the calculated number, because cutting, breakage, and pattern matching all consume extra material. The Tile Council of North America recommends adding a waste factor based on the layout pattern, since the pattern determines how many perimeter tiles must be cut and how large the resulting offcuts are.
| Layout Pattern | Recommended Waste Factor |
|---|---|
| Straight lay (square to wall) | 10% |
| Diagonal (45 degrees) | 15% |
| Herringbone | 15-20% |
| Versailles / French pattern | 20% |
| Complex mosaic with borders | 20-25% |
Larger tiles increase cutting waste because a single offcut near a wall can leave a large unusable piece. Diagonal layouts waste roughly 50 percent more than straight layouts because every perimeter tile is cut at an angle, producing two triangular offcuts instead of one. Always round the final count up to the next full box, because dye lots vary between production runs and matching a discontinued tile months later is often impossible.
Sources: Tile Council of North America (TCNA) installation handbook, American National Standards Institute (ANSI A108/A118) tile installation standards, and manufacturer packaging data. Waste factors reflect typical field conditions; highly irregular rooms with many corners may require an additional 5 percent. The Metriova tile calculator converts dimensions to tile counts and applies the waste factor for each pattern automatically.
Tile Calculator — How Many Tiles for Floor or Wall
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