Tile is counted piece by piece, so a small error in the estimate means either a half-finished floor or boxes of leftovers. This calculator divides the area to be tiled by the space one tile actually occupies — the tile plus its share of grout joint — then adds an allowance for cuts and breakage and rounds up to whole tiles and boxes.
How to use the tile calculator
- Enter the area. For a floor, length × width. For a wall, wall width and tile height. For several walls, add their widths if they share the same height.
- Enter the tile size exactly as sold, for example 12 × 24 in or 30 × 60 cm.
- Enter the grout joint. Floor tile commonly uses 1/8 to 3/16 in; rectified wall tile can go down to 1/16 in. Your tile's packaging usually recommends a width.
- Set the waste allowance — 10% for a straight grid, 15% for diagonal or large-format tile.
- Optional: tiles per box to get the number of boxes.
Tile formula
Tiles = area ÷ space per tile
Tiles to buy = ⌈ tiles × (1 + waste% ÷ 100) ⌉
Boxes = ⌈ tiles to buy ÷ tiles per box ⌉
All measurements must be in the same unit — the calculator converts feet, inches, centimeters and millimeters for you.
Worked example: a 10 × 8 ft bathroom floor
- Area: 10 × 8 = 80 sq ft = 11,520 sq in
- Space per 12 × 12 tile with a 1/8 in joint: 12.125 × 12.125 = 147.02 sq in
- Tiles: 11,520 ÷ 147.02 = 78.4 tiles
- Add 10%: 78.4 × 1.10 = 86.2 → 87 tiles
- At 10 tiles per box: 9 boxes
Tiles per square foot by size
With a 1/8 in grout joint. The last column is for 100 sq ft including 10% waste.
| Tile size | Tiles per sq ft | Tiles for 100 sq ft + 10% |
|---|---|---|
| 3 × 6 in (subway) | 7.52 | 828 |
| 4 × 4 in | 8.46 | 931 |
| 6 × 6 in | 3.84 | 423 |
| 12 × 12 in | 0.98 | 108 |
| 12 × 24 in | 0.49 | 55 |
| 24 × 24 in | 0.25 | 28 |
Tiling tips that affect the count
- Dry-lay the first rows. Centering the layout avoids thin slivers at the walls, which waste tiles and look poor.
- Large-format tile breaks more. Tiles of 24 in and up are harder to cut and handle; lean toward 15% waste.
- Patterned tile needs extra. Encaustic or veined tile may need extra pieces to keep the pattern flowing.
- Check the lot number. Buy all boxes with the same lot or shade code so the color matches.
Laying planks instead? The Flooring Calculator works in boxes and square feet. Need just the area of an odd-shaped room? Use the Square Footage Calculator.
Frequently asked questions
How many 12×12 tiles do I need for 100 square feet?
Exactly 100 tiles if there were no grout lines. With a 1/8 in grout joint each tile covers a little more than a square foot, so it takes about 98 tiles — then add 10% for cuts and breakage, about 108 tiles.
How much extra tile should I buy?
Plan on 10% for a straight grid and 15% for diagonal layouts or large tiles that need many cuts. Keep a few spare tiles after the job — matching a discontinued tile later is difficult.
Does grout width change how many tiles I need?
Slightly. Wider joints mean each tile covers a bit more area, so you need fewer tiles. The effect is small with large tiles and noticeable with small ones like 2 in mosaics.
How do I calculate tile for a shower?
Measure each wall as width × height and add them, plus the floor if it is tiled. Subtract the opening for a niche only if it gets a different tile. Enter the total length and set width to 1 ft, or run each wall separately and add.
How many tiles are in a box?
It depends on the tile size and brand; the box label lists both the count and the square feet covered. If you only know square feet per box, divide your order area by that number instead.