Tile is sold by the box, but installed by the piece — and cut pieces rarely go back together. Getting the count right means knowing your floor area, your tile size, and the waste your chosen layout demands. This guide covers all three and includes a ready-reference chart.
What’s in this guide
The tile count formula
Convert tile size to square feet
Tile is labeled in inches. Convert to square feet before dividing:
| Nominal tile | Area (sq in) | Area (sq ft) | Tiles per sq ft |
|---|---|---|---|
| 6 × 6 in | 36 | 0.25 | 4.00 |
| 12 × 12 in | 144 | 1.00 | 1.00 |
| 12 × 24 in | 288 | 2.00 | 0.50 |
| 18 × 18 in | 324 | 2.25 | 0.44 |
| 24 × 24 in | 576 | 4.00 | 0.25 |
Worked example: tiling a bathroom floor
A 8 ft × 10 ft bathroom floor tiled with 12×24 in tile on a straight layout (10% waste):
| Step | Value |
|---|---|
| Floor area | 8 × 10 = 80 sq ft |
| Tile area | 12 × 24 ÷ 144 = 2.0 sq ft |
| Bare count | 80 ÷ 2.0 = 40 tiles |
| + 10% waste | 40 × 1.10 = 44 tiles |
| Order | 44 tiles (round boxes up) |
Tiles per 100 sq ft by size
| Tile size | Tiles per 100 sq ft | +10% (straight) | +15% (diagonal) |
|---|---|---|---|
| 6 × 6 in | 400 | 440 | 460 |
| 12 × 12 in | 100 | 110 | 115 |
| 12 × 24 in | 50 | 55 | 58 |
| 18 × 18 in | 45 | 50 | 52 |
| 24 × 24 in | 25 | 28 | 29 |
Waste by layout pattern
| Layout | Waste allowance | Notes |
|---|---|---|
| Straight grid | 10% | Fewest cuts |
| Diagonal (45°) | 15% | Triangular offcuts at every wall |
| Brick / offset | 10–12% | Half-tile starts |
| Herringbone | 15–20% | Every course needs cuts |
| Large-format (≥24 in) | 15% | Big, less reusable offcuts |
Tile is boxed in fixed quantities. Convert your tile count to boxes using the pieces-per-box on the label, then round up.
Grout, thinset & spacers
| Material | Rule of thumb |
|---|---|
| Thinset mortar | ~50 sq ft per 50 lb bag (trowel-dependent) |
| Grout | Varies by tile size & joint width — use the bag's coverage chart |
| Spacers | One bag covers a typical room; size sets the joint width |
Common mistakes
Convert tile size to square feet first, or convert the floor to square inches. Never mix.
Order one full box beyond the calculated need — discontinued lines can't be matched later.
A diagonal or herringbone floor can waste 20%. The pattern you pick changes the order.
Key takeaways
- Tiles = (floor area ÷ tile area) × (1 + waste).
- Convert tile size to square feet with (in × in) ÷ 144.
- Waste ranges from 10% straight to 20% herringbone.
- Always keep a full spare box for future repairs.
Related calculators & guides
Frequently asked questions
- How many tiles do I need per square foot?
- Divide 1 by the tile's area in square feet. A 12×12 in tile is 1 sq ft, so you need 1 tile per sq ft. A 6×6 in tile is 0.25 sq ft, so you need 4 per sq ft. Multiply by your floor area and add waste.
- How do I convert tile size in inches to square feet?
- Multiply the two side lengths in inches and divide by 144. A 18×18 in tile = 324 ÷ 144 = 2.25 sq ft.
- How much tile waste should I allow?
- Use 10% for a straight grid, 15% for a diagonal layout, and 15–20% for herringbone or complex patterns. Add extra for small or busy rooms with many cuts.
- Should I buy extra tile for repairs?
- Yes. Keep at least one full box beyond your calculated need. Tile lines are discontinued frequently, and a matching replacement years later is often impossible.