About this calculator
Each tile covers its own face plus half of the grout joint on every side. This tile calculator accounts for that joint, divides your floor or wall area by the space each tile takes, adds a cut-and-breakage allowance and converts the count into boxes.
It works for floor tile, wall tile, shower surrounds, backsplashes and mosaic sheets (enter the sheet size as the tile size).
How to use it
- Enter the length and width of the area. For a wall, use its width and height.
- Enter the tile size as printed on the box (for example 12 × 24 in).
- Enter the grout joint: 1/16 in for rectified tile, ⅛ in for most floor tile, ¼ in for handmade or rustic tile.
- Set the waste allowance and the number of tiles per box.
The formula
Space per tile = (tile length + joint) × (tile width + joint)
Tiles = area ÷ space per tile × (1 + extra%), rounded up
Boxes = tiles ÷ tiles per box, rounded up
For 12 × 12 in tile with a ⅛ in joint, each tile occupies 12.125 × 12.125 in, so you need 0.98 tiles per square foot before waste.
Worked example
These are the calculator’s starting values and the results they produce:
| Area length | 8 ft |
|---|---|
| Area width | 5 ft |
| Tile length | 12 in |
| Tile width | 12 in |
| Grout joint width | 0.125 in |
| Extra for cuts and breakage | 10 % |
| Tiles per box | 10 |
Tips before you buy
- Large-format tile (15 in and up) and patterns like herringbone produce more offcuts — use 15–20% extra.
- Buy enough extra to keep a few spare tiles for future repairs; the same dye lot may not be available later.
- Check that all boxes share the same shade/lot number before you start.
- Dry-lay a row across the room to plan cut sizes at the edges — avoid slivers under half a tile.
Frequently asked questions
How many 12×12 tiles do I need for 100 square feet?
About 98 tiles with a ⅛ in grout joint before waste, or 108 with 10% extra.
How much extra tile should I buy?
10% for a straight lay in a simple room, 15% for diagonal layouts or rooms with many corners, and 20% for herringbone or large-format tile.
How many 12×24 tiles per square foot?
A 12 × 24 in tile covers 2 sq ft, so you need about 0.5 tiles per square foot — about 0.49 with a ⅛ in joint.