How to calculate how many tiles you need
Work out the area to be tiled, divide it by the area of one tile, then add an allowance for cuts and breakage.
Tiles needed = area ÷ tile area × (1 + waste %)
Worked example
A floor 10 feet by 12 feet is 120 square feet. A 12 by 24 inch tile covers 2 square feet, so the floor takes 60 tiles. Adding 10% for waste gives 66 tiles. If a box holds 8 tiles, buy 9 boxes.
Coverage by tile size
| Tile size (inches) | Square feet per tile | Tiles per 100 sq ft |
|---|---|---|
| 4 × 4 | 0.11 | 900 |
| 6 × 6 | 0.25 | 400 |
| 12 × 12 | 1 | 100 |
| 12 × 24 | 2 | 50 |
| 18 × 18 | 2.25 | 45 |
| 24 × 24 | 4 | 25 |
How much waste to allow
- Straight layout in a simple room: 10%.
- Diagonal or herringbone layout: 15%.
- Rooms with many corners or large tiles: 15% or more.
Keep a few spare tiles for repairs. Dye lots vary, so a later batch may not match.
How to use this calculator
Enter the length and width of the floor or wall, the length and width of one tile, the grout gap and a waste allowance. Add the tiles per box from the label. The tile calculator returns the area, the tiles before waste, the tiles needed and the number of boxes to buy.
Finding the area of one tile
Tile sizes are given in inches and room areas in square feet, so convert the tile before you divide:
Tile area in square feet = length (inches) × width (inches) ÷ 144
A 3 by 6 inch tile is 18 ÷ 144 = 0.125 square feet. A 12 by 24 inch tile is 288 ÷ 144 = 2 square feet.
What the result means
The tile count is the area divided by the size of one tile, plus waste, rounded up to a whole tile. The box count rounds up again to whole boxes. That second rounding often leaves a few tiles over, which covers the spares you should keep anyway.
In the worked example, 9 boxes of 8 is 72 tiles against the 66 needed, so 6 are left for repairs.
More examples
A backsplash in small tile
A backsplash of 30 square feet in 3 by 6 inch tile: 30 ÷ 0.125 = 240 tiles. Adding 10% gives 264 tiles.
Shower walls
A shower has one wall 5 feet wide and two walls 3 feet wide, all tiled to 8 feet high. The area is 5 × 8 + 2 × (3 × 8) = 88 square feet. In 12 by 12 inch tile that is 88 tiles. With 15% waste for the corners and cuts, 88 × 1.15 = 101.2, so buy 102 tiles.
The same floor in different tile sizes
This table uses the 120 square foot floor from the worked example with 10% waste.
| Tile size (inches) | Tiles without waste | Tiles with 10% waste |
|---|---|---|
| 6 × 6 | 480 | 528 |
| 12 × 12 | 120 | 132 |
| 12 × 24 | 60 | 66 |
| 18 × 18 | 54 | 59 |
| 24 × 24 | 30 | 33 |
What changes the result
- Tile size. Larger tiles mean fewer pieces. Doubling both sides of a tile cuts the count to a quarter.
- Layout. Diagonal and herringbone patterns need more cuts along every edge.
- Room shape. Corners, niches, toilets and vanities all create offcuts that cannot be reused.
- Box size. The number of tiles per box differs between products, so check the label.
Common mistakes
- Dividing square feet by a tile size in inches without converting the tile to square feet.
- Rounding the tile count or the box count down.
- Using 10% waste for a diagonal layout.
- Buying in two trips. A second batch may come from a different dye lot.
- Forgetting that some boxes are labeled by square feet of coverage instead of by tile count. In that case divide the area with waste by the coverage per box.
Related calculators
For plank and sheet floors, use the flooring calculator. If the walls above the tile are being painted, the paint calculator gives the gallons, and the renovation cost calculator helps budget a full kitchen or bathroom project. Results are estimates, so confirm quantities with your tile supplier or installer.
Frequently asked questions
How many 12 by 12 tiles do I need for 100 square feet?
100 tiles, or 110 with a 10% waste allowance.
Should I subtract grout lines?
For normal grout widths the difference is small and is covered by the waste allowance.
How do I measure a wall for tile?
Multiply the wall’s width by its height, then subtract windows and doors. See the square footage calculator.
How many 12 by 24 tiles do I need for 100 square feet?
50 tiles, or 55 with a 10% waste allowance.
How do I work out the square feet of one tile?
Multiply the tile’s length by its width in inches and divide by 144.
How many tiles come in a box?
It varies by tile size and brand. The box label shows the number of tiles, the square feet covered, or both.
Do I tile under cabinets and appliances?
That is a design choice to settle before you measure. If the tile will stop at the cabinets, leave that area out of the total.