How to calculate how many tiles you need
Start with the area you're covering, then divide it by the space one tile takes up, including its share of the grout line. Finally, add extra for cuts and breakage based on your layout pattern.
Tile footprint = (tile length + grout) × (tile width + grout)
Tiles = area ÷ tile footprint × (1 + waste %)
Example: a 12 × 10 ft bathroom floor is 120 sq ft, or 17,280 square inches. A 12 × 12 inch tile with a 1/8 inch grout joint takes up 12.125 × 12.125 = 147 square inches. That's 117.5 tiles, or 130 tiles once you add 10% for a straight layout.
Tiles per square foot by size
Without grout lines, rounded. Use these to sanity-check a quote or a box label.
| Tile size | Tiles per sq ft | Tiles per 100 sq ft |
|---|---|---|
| 3 × 6 in (subway) | 8 | 800 |
| 4 × 4 in | 9 | 900 |
| 6 × 24 in (plank) | 1 | 100 |
| 12 × 12 in | 1 | 100 |
| 12 × 24 in | 0.5 | 50 |
| 18 × 18 in | 0.44 | 44 |
| 24 × 24 in | 0.25 | 25 |
How much waste to allow
- Straight lay, 10%: tiles in a simple grid. Cuts happen only at the edges.
- Offset or brick pattern, about 12%: staggered joints create more end cuts.
- Diagonal, 15%: every edge tile is cut at an angle.
- Herringbone, 20%: the most cutting of any common pattern.
Add a little more for small or oddly shaped rooms, natural stone (which varies piece to piece), or if you're new to tiling. Keep leftover tiles: matching a discontinued tile years later is often impossible.
Buying tips
- Check that every box has the same batch or lot number. Colors can shift noticeably between batches.
- Round up to whole boxes. Most stores sell tile by the box, not by the piece.
- Dry-lay a row before setting tile to see where your cuts will land and adjust your starting line.
Frequently asked questions
How much extra tile should I buy?
Buy about 10% extra for a straight-lay pattern and 15% or more for diagonal, herringbone or other patterns with lots of angled cuts. The extra also leaves you spare tiles from the same production batch for future repairs.
Do grout lines change how many tiles I need?
Slightly. Each grout joint adds a little width to every tile's footprint, so you need fewer tiles. With large tiles and thin joints the difference is tiny; with small tiles like 3 × 6 subway, a 1/8 inch joint can reduce the count by several percent.
How many tiles are in a box?
It varies by product and tile size, so check the label. Many boxes are sold by coverage, such as 10 to 16 square feet per box. Enter either the tiles per box or the square feet per box above and the calculator works out how many boxes to buy.
How do I measure a room for tile?
Measure the length and width of the floor at its widest points and multiply them. For L-shaped rooms, split the floor into rectangles, calculate each one and add them together. Don't subtract for small areas like toilet flanges; you'll lose that much in cuts anyway.
How do I calculate tile for a backsplash?
Measure the length of the wall section and the height from countertop to the bottom of the cabinets, then multiply. Subtract large openings like windows, but keep outlets in, since cutting around them wastes tile.