DIY Home CalcsTile Calculator
Calculate how many tiles you need for a floor, shower wall or backsplash. Enter the area, your tile size and the grout joint, then add a waste allowance for cuts. If you know how many tiles come in a box, you also get the number of boxes.
How the tile calculation works
Each tile, plus half a grout joint on every side, occupies a small rectangle of floor. Divide the area by that rectangle and you have the number of tiles. Then add the waste allowance and round up.
tiles = area ÷ coverage per tile × (1 + waste %)
The 144 converts square inches to square feet. Tiles are sold whole, so the result always rounds up.
Worked example: a bathroom floor
A 5 ft × 8 ft bathroom is 40 sq ft. With 12 × 24 in porcelain tile and a 1/8 in joint:
- Coverage per tile: 12.125 × 24.125 ÷ 144 ≈ 2.03 sq ft.
- Tiles without waste: 40 ÷ 2.03 ≈ 19.7, so 20 tiles.
- With 15% waste (small room, many cuts around the toilet and vanity): about 23 tiles.
- At 8 tiles per box, buy 3 boxes.
How much waste to allow
| Layout | Suggested waste |
|---|---|
| Straight grid, simple rectangular room | 10% |
| Brick / offset pattern | 10–15% |
| Diagonal or herringbone | 15–20% |
| Small room with many obstacles | 15% |
| Large-format tile (24 in and up) | 15–20% |
More detail is in our guide on how much extra material to buy.
Common tile sizes
| Tile size | Sq ft per tile | Tiles per 100 sq ft (no waste, no joint) |
|---|---|---|
| 3 × 6 in subway | 0.125 | 800 |
| 4 × 4 in | 0.111 | 900 |
| 6 × 24 in plank | 1.0 | 100 |
| 12 × 12 in | 1.0 | 100 |
| 12 × 24 in | 2.0 | 50 |
| 24 × 24 in | 4.0 | 25 |
Tips
- Buy all the tile at once and check that the boxes share the same lot or shade number.
- For mosaic sheets, enter the sheet size (often 12 × 12 in) instead of the individual chip size.
- Tiling the floor and then laying new flooring elsewhere? The flooring calculator handles several rooms at once.
Frequently asked questions
How many 12x12 tiles do I need for 100 square feet?
Each 12 × 12 in tile covers 1 sq ft, so 100 sq ft needs 100 tiles before waste. With a 10% allowance for cuts and breakage, buy 110 tiles.
How much extra tile should I buy?
Add 10% for a straight layout in a simple room, 15% for diagonal or herringbone patterns or rooms with many corners, and up to 20% for large-format tile, where one bad cut wastes a big piece.
Does grout width change the number of tiles?
Slightly. Grout joints add to the space each tile occupies, so you need a few fewer tiles. With small mosaic or 4 in tiles and wide joints the difference matters more; for large tiles with 1/16 in joints it is negligible.
How do I calculate tile for a backsplash?
Measure the length of the counter run and the height from the counter to the bottom of the cabinets, multiply them for square feet, and subtract any large windows. Typical backsplashes are 18 in tall.
Should I keep leftover tile?
Yes. Keep at least one box. Tile lines are discontinued and dye lots change, so a matching replacement can be impossible to find years later.