Tile Calculator
Enter the size of your floor or wall, choose a tile and grout joint, and add a waste allowance. You get the exact number of tiles, how many to buy, the boxes and an optional cost.
How to use the Tile Calculator
- Choose units (feet or meters) and whether you are tiling a floor or a wall.
- Enter the dimensions. Add extra areas for L-shaped rooms, or add doors and windows to deduct on a wall.
- Pick the tile size and enter the grout joint width, for example 1/8 in or 3 mm.
- Set the waste allowance: 10% for a straight lay, 15% for diagonal or herringbone.
- Optionally enter the box size and price to get the number of boxes and the total cost.
The tile formula
Every tile covers its own face plus half a grout joint on each side, which works out to one full joint in each direction. So the area one tile really covers is:
coverage per tile = (tile width + joint) × (tile length + joint)
tiles needed = area ÷ coverage per tile × (1 + waste %) , rounded up
Example: a 12 × 10 ft kitchen floor is 120 sq ft. A 12 × 24 inch tile with a 1/8 inch joint covers 12.125 × 24.125 = 292.5 sq in, or 2.031 sq ft. That gives 120 ÷ 2.031 = 59.1 tiles. Adding 10% waste makes 65.0, so you buy 65 tiles. If a box holds 8 tiles, that is 65 ÷ 8 = 8.1, so 9 boxes.
Tiles per square foot and square meter
Tile counts per unit of area for common sizes, without waste. The joint makes little difference for big tiles but matters for small mosaics and subway tiles.
| Tile size | Area per tile | Tiles per 100 sq ft (no joint) | Tiles per 100 sq ft (1/8 in joint) | Tiles per m² |
|---|---|---|---|---|
| 4 × 4 in | 0.111 sq ft | 900 | 846 | 96.9 |
| 3 × 6 in subway | 0.125 sq ft | 800 | 752 | 86.1 |
| 6 × 24 in plank | 1 sq ft | 100 | 97.5 | 10.8 |
| 12 × 12 in | 1 sq ft | 100 | 97.9 | 10.8 |
| 12 × 24 in | 2 sq ft | 50 | 49.2 | 5.38 |
| 18 × 18 in | 2.25 sq ft | 44.4 | 43.8 | 4.78 |
| 24 × 24 in | 4 sq ft | 25 | 24.7 | 2.69 |
| 30 × 30 cm | 0.09 m² | 103 | 101 | 11.1 |
| 30 × 60 cm | 0.18 m² | 51.6 | 50.8 | 5.56 |
| 60 × 60 cm | 0.36 m² | 25.8 | 25.5 | 2.78 |
How much waste to allow for
| Layout | Waste allowance | Why |
|---|---|---|
| Straight grid, large simple room | 5–10% | Cuts only along the edges |
| Straight or brick (offset) lay | 10% | The usual default for floors and walls |
| Diagonal (45°) | 15% | Every edge tile is cut at an angle |
| Herringbone or chevron | 15–20% | Many angled cuts and more breakage |
| Small room, many corners, natural stone | 15–20% | More cuts and pieces rejected for color or flaws |
Buy all boxes from the same production batch (shade or lot number) so the color matches, and keep a few spare tiles for future repairs.
Measuring tips
- Measure each wall or floor section at its widest point and round up to the next inch or centimeter.
- Split L-shaped and irregular rooms into rectangles and add each one as a separate area.
- For a shower or backsplash, measure each wall separately in Wall mode and deduct windows, but not small outlets.
- Remember extra pieces for trim, bullnose edges or a skirting row: these are usually sold by the linear foot.
Frequently asked questions
How many tiles do I need for 100 square feet?
With 12×12 inch tiles and a 1/8 inch joint, 100 sq ft needs about 98 tiles before waste, or 108 tiles with 10% waste. Each tile covers 1 sq ft, so without joints you need 100 tiles, and 110 with a 10% allowance.
How much extra tile should I buy?
Buy about 10% extra for a straight or brick-pattern lay and 15% for diagonal, herringbone or chevron patterns. Add more for small rooms with many cuts, large-format tiles or natural stone with color variation. Keeping a few spare tiles also helps with future repairs.
How many 12×24 tiles are in a box?
It varies by manufacturer, but a box of 12×24 inch tiles usually holds 6 to 8 tiles, covering about 12 to 16 square feet. Check the label: it lists both the tile count and the square footage per box, and you can enter either in the calculator.
Does grout width affect how many tiles I need?
Yes. Each tile effectively covers its own size plus one grout joint in each direction. The effect is small for large tiles but adds up for small ones: 4×4 inch tiles with 1/8 inch joints cover about 6% more area each, so you need about 6% fewer tiles.
How do I calculate tiles for a wall with a window?
Measure the wall width and height, multiply them for the gross area, then subtract the area of each door and window. Divide the result by the area one tile covers including grout, add waste and round up. Use Wall mode and add each opening to do this automatically.
How many tiles do I need per square meter?
A 30×30 cm tile covers 0.09 m², so you need about 11.1 tiles per square meter, or roughly 10.9 with a 3 mm joint. For 60×60 cm tiles it is about 2.8 per m², and for 30×60 cm about 5.6 per m², before waste.