How this calculator works
Each tile covers its own face plus half a grout joint on every side. The calculator divides the area (plus a pattern-specific waste allowance) by that coverage to count tiles, then converts the tile area into full boxes.
Coverage per tile = (Tile L + Joint) × (Tile W + Joint) ÷ 144
Tiles = round up( Area × (1 + Waste%/100) ÷ Coverage per tile )
Boxes = round up( Tiles × Tile area ÷ Box coverage )
Assumptions and tips
- Waste rises with pattern complexity: about 10% for straight and offset layouts, 15% for diagonal and 20% for herringbone.
- Rooms with many corners, pipes or a large-format tile may need more.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Area length | 10 ft |
| Area width | 8 ft |
| Tile length | 24 in |
| Tile width | 12 in |
| Grout joint | 0.125 in |
| Layout pattern | Straight grid (10% waste) |
| Coverage per box | 16 sq ft |
| Result | Value |
|---|---|
| Tiles needed | 44 tiles |
| Boxes to buy | 6 boxes |
| Floor/wall area | 80 sq ft |
| Waste allowance used | 10 % |
| Area covered by one tile + joint | 2.031 sq ft |
Step by step:
- Area = 80 sq ft; + 10% for this pattern = 88 sq ft
- Each tile + joint covers 2.031 sq ft
- Tiles = 88 ÷ 2.031 → 44
- Boxes = 44 × 2 sq ft ÷ 16 → 6
Tiles per 100 sq ft by tile size
1/8 in grout joint, straight layout with 10% waste.
| Tile size | Tiles per 100 sq ft |
|---|---|
| 12 × 12 in | 108 tiles |
| 12 × 24 in | 55 tiles |
| 18 × 18 in | 49 tiles |
| 24 × 24 in | 28 tiles |
| 6 × 24 in plank | 108 tiles |
| 3 × 6 in subway | 828 tiles |
Common mistakes to avoid
- Buying tile from different lots — shade can differ visibly.
- Using straight-lay waste for a herringbone or diagonal layout.
Frequently asked questions
How much extra tile should I buy?
Typically 10% for straight layouts and 15–20% for diagonal or herringbone patterns.
Does the grout joint really matter?
Slightly — wider joints mean each tile covers a little more area, so you need a few fewer tiles.