Updated June 17, 2026
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To calculate tiles needed: find the room's square footage (length x width), divide by the square footage of one tile, then add 10 percent for waste -- 15 percent for diagonal or pattern layouts. For a 120-square-foot bathroom with 12x12 tiles (1 sq ft each), you need 120 tiles plus 12 for waste = 132 tiles minimum.
Tile size to square footage conversion
| Tile size | Sq ft per tile | Tiles per 100 sq ft (before waste) |
|---|---|---|
| 6 x 6 in | 0.25 sq ft | 400 |
| 12 x 12 in | 1.00 sq ft | 100 |
| 12 x 24 in | 2.00 sq ft | 50 |
| 18 x 18 in | 2.25 sq ft | 44 |
| 24 x 24 in | 4.00 sq ft | 25 |
| 3 x 6 in subway | 0.125 sq ft | 800 |
The tile quantity formula
- Measure the area to tile: length x width in feet = square feet.
- Find the tile's square footage: multiply tile length (in feet) x tile width (in feet). For a 12x12 tile, that is 1 x 1 = 1 sq ft.
- Divide area by tile size: 120 sq ft / 1 sq ft = 120 tiles.
- Add 10% waste: 120 x 1.10 = 132 tiles.
- Round up to the nearest box quantity.
Why 10 percent is not always enough
Add 15 percent if the tiles are set diagonally, the room has many corners or cut-outs, or the tile is large (24x24 and up) because edge cuts waste more of each tile. Oddly shaped bathrooms and kitchens with islands or peninsulas also benefit from the higher buffer. Use our tile calculator to enter your layout and get a precise count including grout joint width.
Do not forget grout and spacers
Tile coverage does not include grout joints. For a standard 1/8-inch grout joint, the spacing has minimal impact on tile count but matters for grout quantity. Grout coverage varies by tile size and joint width; the bag label typically states coverage in square feet. Tile spacers come in packs and are consumed per intersection, so buy one pack per 50 to 100 square feet as a starting point.
Backsplash and wall tile tips
Wall and backsplash tiles are usually sold by the square foot. Measure the backsplash area (length x height between counter and upper cabinets), subtract outlet and switch cutouts (about 0.5 sq ft each), and add 10 percent. Wall tiles break more easily than floor tiles, so a slightly higher waste factor (12 to 15 percent) is wise. See how to measure square footage for odd shapes.
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