The Floor Tile Calculator calculates how many tiles and boxes you need to tile a floor.
It divides the floor area by the space each tile takes up including its grout joint — (tile width + joint) × (tile length + joint) — adds waste, rounds up and converts to boxes. If you already know your floor area, use the second mode.
Floor Tile Calculator
How many floor tiles and boxes you need for any tile size and grout joint, with waste.
Formula
- Tiles: ⌈L × W ÷ ((tw + j) × (tl + j)) × (1 + waste %)⌉
- Boxes: ⌈tiles ÷ tiles per box⌉
- From area: ⌈A ÷ (tw × tl) × (1 + waste %)⌉
Where tw, tl = tile width and length, j = grout joint.
How the Calculation Works
Step 1: Find the floor area.
Step 2: Divide by the area one tile covers including its joint.
Step 3: Add waste, round up, and divide by tiles per box.
Variables Explained
| Input | Meaning |
|---|---|
| Tile width, length | Tile size, e.g. 12 × 24 in |
| Grout joint | Space between tiles |
| Tiles per box | From the box label |
Example Calculation
Given: room 15 × 12 ft, 12 × 24 in tiles, 3/16 in joints, 10% waste, 8 per box
Tile + joint: 12.1875 × 24.1875 in ≈ 2.047 ft²
Tiles: 180 ÷ 2.047 × 1.1 ≈ 96.7 → 97 tiles
Result: 97 tiles = 13 boxes
Tiles per Square Foot
| Tile size | Tile area | Tiles per 100 ft² (no joint, no waste) |
|---|---|---|
| 12 × 12 in | 1 ft² | 100 |
| 12 × 24 in | 2 ft² | 50 |
| 18 × 18 in | 2.25 ft² | 45 |
| 24 × 24 in | 4 ft² | 25 |
| 6 × 24 in | 1 ft² | 100 |
Material Estimation Notes
Thinset, grout, spacers, backer board or membrane are separate. Buy all tiles from the same lot so shade and size match, and keep a few for future repairs.
Waste Factor Considerations
Waste depends on tile size, layout (straight, offset, diagonal, herringbone), the number of cuts around the room’s edges and fixtures, and breakage. Large-format tiles and diagonal layouts usually need more.
Frequently Asked Questions
How many tiles do I need?
Floor area ÷ tile area (with joint), plus waste.
How many 12 × 24 tiles for 100 square feet?
50 tiles before waste and joints.
Does grout width change the tile count?
Slightly — wider joints mean fewer tiles.
How many boxes of tile do I need?
Tiles needed ÷ tiles per box, rounded up.
Should I subtract cabinets?
Only if you won’t tile under them; check whether your installer tiles under appliances.