To work out how many tiles you need, multiply the room's length by its width to get the area in square feet, then divide by the area of a single tile, and add about 10% for waste. For example, a 10 ft by 12 ft floor is 120 square feet, so with 12-inch tiles (1 square foot each) you need 120 tiles, or roughly 132 once you allow for cuts and breakage. The two numbers that decide everything are your floor area and your tile size, so measure carefully and check the tile dimensions on the box before you buy.
How do you calculate how many tiles you need?
The whole calculation comes down to one idea: how many tiles fit into your floor area. The formula is:
Tiles = Floor area ÷ area of one tile, then add waste
Work in consistent units. The easiest approach is to convert everything to feet:
- Measure the room's length and width in feet and multiply them for the floor area in square feet. If you are unsure how to measure an irregular space, the square feet calculator walks through it.
- Find the area of one tile. A 12-inch by 12-inch tile is exactly 1 square foot. A 6-inch tile is 0.25 square feet, and an 18-inch tile is 2.25 square feet.
- Divide the floor area by the tile area to get the raw tile count.
- Add a waste allowance (usually 10%) and round up to whole tiles, then up again to full boxes.
If you would rather skip the arithmetic, enter your room size and tile size into the tile calculator and it returns the count, including waste, instantly.
How many tiles come in a box?
Tile is sold by the box, and boxes are labelled by the total area they cover rather than a fixed tile count. Coverage varies by tile size, so the number of tiles per box changes too. These are typical ranges you will see at suppliers like The Home Depot:
| Tile size | Area per tile | Typical coverage per box | Tiles per box (approx.) |
|---|---|---|---|
| 6 in × 6 in | 0.25 ft² | 10–12 ft² | 40–48 |
| 12 in × 12 in | 1.0 ft² | 10–15 ft² | 10–15 |
| 18 in × 18 in | 2.25 ft² | 15–18 ft² | 7–8 |
| 12 in × 24 in | 2.0 ft² | 14–16 ft² | 7–8 |
Always read the coverage figure printed on the box, then divide your total square footage (with waste added) by that number and round up. Buying by the box is also why a small waste allowance often rounds up to a whole extra box, which is normal and gives you useful spares.
How much extra tile should you buy for waste?
Every tile job produces offcuts at the walls and around obstacles, plus the odd tile that cracks during cutting or setting. The Tile Council of North America and most installers recommend ordering extra so you do not run short mid-job, because matching a dye lot later is difficult. A widely used industry rule of thumb is an overage of around 10% for simple layouts. Guides such as This Old House give the same advice.
Use these allowances as a starting point:
- Straight (grid) layout: add 10%.
- Diagonal layout: add 15%, because angled cuts at every edge waste more.
- Herringbone or chevron: add 15% to 20%, since each tile is cut at the perimeter.
- Rooms with lots of corners, alcoves, or pipework: lean toward the higher end.
Whatever pattern you choose, keep a few full tiles from the same batch after the job. A future chip or crack is far easier to repair when you have a perfect colour match on hand.
How do tile size and layout change the count?
Tile size has the biggest effect on how many pieces you handle. Larger tiles cover more area each, so you need fewer of them, which usually means faster installation and fewer grout lines. Smaller tiles and mosaics cover less per piece, so the count climbs quickly.
Here is the same 120 square foot floor estimated with three common tile sizes, before waste:
- 12 in tiles (1 ft²): 120 ÷ 1 = 120 tiles
- 6 in tiles (0.25 ft²): 120 ÷ 0.25 = 480 tiles
- 18 in tiles (2.25 ft²): 120 ÷ 2.25 = 54 tiles
Layout matters too. A straight grid is the most material-efficient. Diagonal and herringbone patterns look great but cut more tiles at the edges, which is why their waste allowance is higher. If you are tiling a floor as part of a wider flooring project, the flooring calculator helps you compare tile against other floor coverings on the same area.
How do you measure a room for tile?
Accurate measurements are what keep your estimate honest. Follow these steps:
- Split the room into rectangles. Measure the length and width of each rectangle in feet and inches.
- Multiply and add. Calculate each rectangle's area (length × width) and add them together for the total floor area.
- Subtract large fixed features only. Take out the footprint of anything you will not tile, such as a kitchen island base or a built-in tub. Do not bother subtracting small items.
- Convert tile dimensions to feet. Divide the tile's inches by 12, so a 12-inch tile is 1 ft and an 8-inch tile is 0.667 ft.
- Apply the formula and add waste. Divide area by tile area, add 10% to 15%, and round up to full boxes.
Worked example
Say you are tiling an L-shaped kitchen floor. The main area is 12 ft by 10 ft, and a smaller section is 6 ft by 4 ft.
- Main area: 12 × 10 = 120 ft²
- Small section: 6 × 4 = 24 ft²
- Total floor area: 120 + 24 = 144 ft²
- Using 12-inch tiles (1 ft² each): 144 ÷ 1 = 144 tiles
- Add 10% waste: 144 × 1.10 = 158.4, round up to 159 tiles
- If a box covers 12 ft², you need 144 × 1.10 ÷ 12 = 13.2, so buy 14 boxes
That is the entire process. Measure the area, divide by the tile size, add a waste allowance, and round up to whole boxes.
Common tile-counting mistakes to avoid
A few small errors account for most cases of running short or massively over-buying:
- Forgetting to add waste. Ordering the exact area count leaves no margin for cuts or breakage, and you will almost certainly come up short.
- Mixing up tile and room units. A 12-inch tile is 1 foot, not 12 feet. Convert both the room and the tile to the same unit before dividing.
- Buying across dye lots. Tiles from different production batches can vary slightly in shade. Buy your full quantity, including spares, in one order from the same lot.
- Ignoring the box size. A waste allowance often pushes you into one more box. Work out the box count, not just the tile count, before checkout.
- Tiling walls at the floor allowance. Wall layouts around niches, windows, and trim usually need a touch more overage than a plain floor.
Avoiding these keeps your single order accurate, which saves both a second trip and the risk of a visible colour mismatch.
Get your exact tile count
Plug your own room and tile dimensions into the tile calculator to get the number of tiles and boxes you need, with the waste allowance already built in. It is free, works for floors and walls, and handles any tile size.