Quick answer:Divide the area you’re tiling (length × width, in square feet) by the area one tile covers, add 10–15% for waste, and round up to full boxes. For example, a 120 sq ft floor with 12×12 in tiles (1 sq ft each) needs 120 tiles, plus about 12 for waste — 132 tiles total.
That one line covers most projects. The rest of this guide shows each step, three real examples, and the mistakes that cause people to run short. If you’d rather skip the math, the tile calculator does it instantly.
The tile quantity formula
then round up to the nearest whole tile, and again to full boxes.
Step 1: Measure the area in square feet
Measure the length and width of each surface in feet and multiply them. For rooms that aren’t simple rectangles, break them into rectangles and add the areas together.
Working in metric? Measure in meters (a 2.4 m × 3 m room is 7.2 sq m). The calculator accepts both and converts for you.
Step 2: Find the area of one tile
Multiply the tile’s length and width, then convert to square feet by dividing by 144 (there are 144 square inches in a square foot).
| Tile size | Square feet per tile |
|---|---|
| 3 × 6 in (subway) | 0.125 |
| 6 × 6 in | 0.25 |
| 12 × 12 in | 1.00 |
| 12 × 24 in | 2.00 |
| 24 × 24 in | 4.00 |
Step 3: Divide to get the base tile count
Step 4: Add waste (10–15%)
You always need extra tile for edge cuts, breakage, and future repairs. Use 10% for straight layouts and 15% for diagonal or patterned ones. Our guide on how much extra tile to buy breaks this down by layout.
Step 5: Convert tiles to boxes
Tile is sold by the box. Divide your total tiles by the tiles per box and round up — never down, or you’ll come up short.
Worked examples
10 × 10 ft bedroom floor, 12×12 tiles
Base tiles: 100 · +10% waste: 10 → 110 tiles
At 15 tiles per box: 7.33 → 8 boxes
14 × 11 ft kitchen floor, 12×24 tiles
Base tiles: 154 ÷ 2 = 77 · +10% waste: 8 → 85 tiles
At 6 tiles per box: 14.17 → 15 boxes
Bathroom wall with a window (metric)
Net area: 5.76 − 1.08 = 4.68 sq m · Tile: 30×60 cm = 0.18 sq m
Base tiles: 4.68 ÷ 0.18 = 26 · +10%: 3 → 29 tiles
Common mistakes that leave you short
- Rounding down. Always round tiles and boxes up.
- Buying the exact count. Skipping the waste allowance almost guarantees a second trip.
- Forgetting the pattern. Diagonal and herringbone layouts need more tile than a straight grid.
- Mixing dye lots. Buy all your tile in one order so the color matches.
Frequently asked questions
- How many 12x12 tiles do I need for 100 square feet?
- A 12x12 inch tile covers exactly 1 square foot, so 100 square feet needs 100 base tiles. Adding the standard 10% waste gives 110 tiles for a straight layout. Always round up to full boxes.
- How much extra tile should I add for waste?
- Add about 10% for straight or grid layouts and 15% for diagonal, herringbone, or chevron patterns. Increase to 15-20% for natural stone, small mosaics, or first-time DIY installs.
- Do I buy tile by the square foot or by the tile?
- Tile is sold in boxes, each covering a set number of tiles or square feet. Work out your total tiles (including waste), then divide by the tiles per box and round up to the next full box.
- How do I calculate tiles for an L-shaped or irregular room?
- Split the space into rectangles, calculate each rectangle's area separately, add them together, then apply the normal tile calculation. The calculator's 'Add Another Area' button does this for you.
Ready to run your own numbers? Our tile calculator handles multiple areas, opening deductions, grout spacing, and box counts in one step. For floor-specific tips, see how to calculate tiles for a floor.
Ready to calculate your tiles?
Use our free tile calculator to calculate how many tiles you need for any project in seconds.
Use the Tile Calculator