Quick answer: measure the area to tile in square feet or square metres, divide by the area of one tile (including its grout joint), then add 10% for a straight layout, 15% for diagonal and 15–20% for herringbone. Round up to whole boxes. The tile calculator does it in one step.
1. Measure each area
- Floors: length × width. Split L-shapes into rectangles.
- Walls and showers: width × height of each wall, measured separately. Include the shower floor, niches and the bench top if you’re tiling them.
- Splashbacks: width × height of the tiled area.
Small openings, like a single door, can stay in. The extra helps cover cuts. Subtract large windows and patio doors.
2. Tiles per square foot or metre
| Tile size | Per sq ft (1/8” joint) | Per m² (3 mm joint) |
|---|---|---|
| 4 × 4” (100 × 100 mm) | about 8.5 | about 94 |
| 12 × 12” (300 × 300 mm) | about 0.98 | about 10.9 |
| 12 × 24” (300 × 600 mm) | about 0.49 | about 5.5 |
| 24 × 24” (600 × 600 mm) | about 0.25 | about 2.8 |
3. Add waste
| Layout | Add |
|---|---|
| Straight grid | 10% |
| Brick / offset | 10–15% |
| Diagonal | 15% |
| Herringbone | 15–20% |
Large-format tiles (24” or 600 mm and up) break more easily and each loss costs more, so lean toward the higher end.
4. Convert to boxes
Divide the number of tiles by the tiles per box (it’s on the label) and round up. Buy everything from the same batch: shade and size can vary between production runs.
5. Adhesive and grout
These depend heavily on the tile size and the trowel notch, so check the product label. As a rough guide:
- Thinset / tile adhesive: larger tiles need a bigger trowel notch, so more adhesive per square foot. Bag coverage can vary from roughly 40 to 90+ sq ft for the same bag.
- Grout: narrow joints and big tiles need very little. Small mosaics with wide joints need much more. Most grout makers publish a coverage chart by tile size and joint width.
Worked example: a 10 × 8 ft bathroom floor
| Step | Result |
|---|---|
| Area | 10 × 8 = 80 sq ft |
| Tile | 12 × 24” with a 1/8” joint, about 0.49 tiles per sq ft |
| Tiles before waste | 80 × 0.49 ≈ 39.4 |
| Plus 10% | about 44 tiles |
| Boxes of 8 | 44 ÷ 8 = 5.5, so 6 boxes |
FAQ
How much extra tile should I buy?
10% for straight layouts, 15% for diagonal and up to 20% for herringbone. Keep a few spare tiles for repairs.
How do I measure for shower tile?
Measure each wall (width × height) and the floor separately, plus any niche, and add them together.
Do I need more tile for a herringbone pattern?
Yes, about 15–20% extra, because every edge row is cut at an angle.
What else will I need?
Tile adhesive, grout, spacers, a notched trowel, a tile cutter or wet saw, and levelling compound if the floor isn’t flat. If you’re also replacing the floor elsewhere, try the flooring calculator.
How this guide was written: waste allowances and tile counts are standard industry rules of thumb. Always follow the tile and adhesive makers’ instructions. See how I test and review.