How to work out how many tiles you need
- Measure the length and width of the floor, or of each wall, and multiply to get the area.
- Work out the area of one tile. A 12 × 12 inch tile is 1 sq ft; a 300 × 600 mm tile is 0.18 m².
- Add the overage for your pattern, then divide by the tile area and round up.
- Divide by the number of tiles in a box and round up again.
tiles = area × (1 + waste %) ÷ area of one tile
Worked example
An 8 × 10 ft bathroom floor is 80 sq ft. With 12 × 12 inch tiles laid straight, add 10 percent: 88 sq ft, so 88 tiles. At 10 tiles per box, order 9 boxes.
How much extra tile to buy
Cuts at walls, around toilets and at doorways all produce offcuts you cannot reuse. The more angled cuts a pattern needs, the more you waste.
| Pattern | Extra to add |
|---|---|
| Straight grid | 10% |
| Offset / brick bond | 10 to 15% |
| Diagonal | 15% |
| Herringbone | 15 to 20% |
Large-format tiles in small rooms also waste more, because each cut throws away a bigger piece.
Tips before you order
- Check that all boxes share the same batch or shade code. Tiles from different batches can vary in colour and size.
- Keep one spare box. If a tile cracks in five years, the same product may no longer be made.
- For walls, measure each wall separately and subtract windows, the bath and the shower tray.
- For L-shaped rooms, split the floor into rectangles and add the areas together.
Frequently asked questions
How many 12 × 24 tiles do I need for 100 square feet?
Each 12 × 24 inch tile covers 2 sq ft, so 100 sq ft needs 50 tiles. With 10 percent extra, buy 55.
How much extra tile should I buy?
Plan for at least 10 percent on a simple straight layout, 15 percent for diagonal, and up to 20 percent for herringbone or rooms with many corners.
Do grout lines change the number of tiles?
Slightly. Grout joints mean each tile covers a bit more area, so ignoring them, as this calculator does, gives you a small extra margin.
Can I use this for backsplashes?
Yes. Enter the backsplash length and height as the area, then subtract any outlets or windows by reducing the size.
Last updated November 1, 2026.