How to calculate tiles
- Measure the area in feet. For walls, use width × height; for L-shaped floors, split into rectangles and add them (or use our square footage calculator).
- Enter the tile size and grout joint. The joint slightly increases the area each tile covers, which matters for small tiles.
- Add waste for cuts and breakage, and enter tiles per box to see how many boxes to buy.
Tile formula
Tiles = Area ÷ Area per tile × (1 + waste %)
Worked example
A 10 × 8 ft bathroom floor is 80 sq ft. A 12 × 12 in tile with a ⅛ in joint covers about 1.021 sq ft, so the floor needs 78.4 tiles. With 10% waste, buy 87 tiles.
How much extra tile to buy
| Layout | Typical extra |
|---|---|
| Straight / grid | 10% |
| Offset or brick (running bond) | 10–15% |
| Diagonal | 15% |
| Herringbone or chevron | 15–20% |
| Many corners, niches or small rooms | Add 5% more |
Extra tile from the same production lot (check the dye lot or shade number on the box) is worth keeping for future repairs.
Tiles per 100 sq ft
| Tile size | Sq ft per tile | Tiles (no waste, no grout) | Tiles + 10% |
|---|---|---|---|
| 4 × 4 in | 0.111 | 900 | 990 |
| 6 × 6 in | 0.250 | 400 | 440 |
| 12 × 12 in | 1.000 | 100 | 110 |
| 12 × 24 in | 2.000 | 50 | 55 |
| 18 × 18 in | 2.250 | 45 | 49 |
| 24 × 24 in | 4.000 | 25 | 28 |
| 6 × 24 in | 1.000 | 100 | 110 |
| 8 × 48 in | 2.667 | 38 | 42 |
Grout joint widths
- Rectified porcelain: often ⅛ in or as narrow as 1/16 in.
- Standard floor tile: ⅛–¼ in.
- Rustic or handmade tile: ¼–½ in to absorb size variation.
Follow the tile manufacturer's minimum joint — large-format tiles need a joint wide enough to account for slight warpage.
Frequently asked questions
How many tiles do I need for 100 square feet?
With 12 × 12 in tiles, 100 tiles cover 100 sq ft; add 10% and buy 110. With 12 × 24 in tiles you need 50, or 55 with 10% extra.
How do I calculate how many tiles I need?
Divide the area in square feet by the area of one tile in square feet (length × width in inches ÷ 144). Add 10–15% for cuts and breakage, then round up to whole boxes.
Should I include grout lines in the calculation?
For accuracy, yes — the joint adds to the space each tile covers. The effect is small for large tiles but noticeable for mosaics and small tiles.
How much extra tile should I buy?
10% for straight layouts and 15% or more for diagonal or herringbone patterns. Keep the spare tiles for repairs.
How many boxes of tile do I need?
Divide the number of tiles (including waste) by the tiles per box and round up. Boxes often list the square feet they cover, which you can also divide into your area.