How to use the tile calculator
- Measure the area. For a floor, measure length and width in feet. For a wall or backsplash, measure width and height. Subtract large areas that will not be tiled, such as a tub or a window, or enter the net area directly.
- Enter the tile size in inches. Use the actual size printed on the box. A tile sold as 12 × 24 is usually very close to that.
- Pick the grout joint. Rectified porcelain often uses 1/16 or 1/8 inch. Hand-made and rustic tiles use 3/16 to 3/8 inch.
- Choose the layout. Patterns that need more cuts waste more tile, so the calculator raises the waste allowance automatically.
Tile formula
Tiles = area ÷ tile coverage × (1 + waste %)
Boxes = tiles ÷ tiles per box, rounded up
Worked example
A 10 × 8 ft bathroom floor is 80 sq ft. With 12 × 24 inch tiles and a 1/8 inch joint, each tile covers (12.125 × 24.125) ÷ 144 = 2.03 sq ft. You need 80 ÷ 2.03 = 39.4 tiles, so 40 without waste. With 10% waste for a straight layout, buy 44 tiles. At 8 tiles per box that is 6 boxes.
How much extra tile to buy
| Layout | Extra tile |
|---|---|
| Straight grid, simple room | 10% |
| Offset or brick pattern | 10% to 15% |
| Diagonal | 15% |
| Herringbone or chevron | 20% or more |
| Large format (24 in and up) | Add 5% more, breakage costs more |
Keep a few spare tiles after the job. Discontinued tiles are impossible to match years later when one cracks.
Common tile sizes and coverage
| Tile size | Tiles per 100 sq ft (1/8 in joint, no waste) |
|---|---|
| 3 × 6 in subway | about 760 |
| 12 × 12 in | about 98 |
| 12 × 24 in | about 50 |
| 24 × 24 in | about 25 |
| 6 × 36 in wood-look plank | about 66 |
Need the floor area of an odd-shaped room first? Use the square footage calculator, then enter the total here.
Frequently asked questions
How many tiles do I need for 100 square feet?
With 12 × 12 inch tiles and a 1/8 inch joint you need about 98 tiles, or 108 with 10% waste. With 12 × 24 inch tiles you need about 50, or 55 with waste.
How much extra tile should I buy?
Buy 10% extra for straight layouts, 15% for diagonal and 20% for herringbone or chevron patterns.
Do grout lines affect how many tiles I need?
Slightly. Wider joints mean each tile covers a little more area, so you need fewer tiles. With small tiles and wide joints the difference can reach 5% or more.
How many square feet are in a box of tile?
It varies by size and brand, typically 8 to 16 square feet per box for floor tile. Check the label, or enter the tiles per box above to get a box count.
How do I calculate tile for a wall?
Multiply the wall width by the height you will tile, subtract windows and doors, and enter the result as the area. Backsplashes are usually 18 inches tall between countertop and upper cabinets.
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Last updated October 2026.