Running out of tile halfway through a job is worse than having a few left over — a later batch can differ in shade. This tile calculator works out how many tiles and boxes to buy for a floor, wall or backsplash. Enter the area size, the tile size in inches or centimetres, a waste allowance and how many tiles come in a box, and it rounds everything up to whole tiles and whole boxes, with an optional cost.
The calculator divides the area by the face size of one tile. It ignores grout joints, which makes the count slightly conservative — a small, deliberate safety margin. Tiling over a new slab? Size the concrete first with the concrete slab calculator.
How to use the tile calculator
- Measure the length and width of the floor or wall section. For L-shaped rooms, calculate each rectangle separately and add them up.
- Enter the tile's length and width. Use the unit menus for inches or centimetres; a 30 × 60 cm tile is about 11.8 × 23.6 in.
- Set the waste allowance: about 10% for a straight lay, 15% for diagonal or herringbone patterns, and more for small, irregular rooms.
- Enter tiles per box from the product label to get the number of boxes.
- Optionally enter the price per square foot to see the cost of the boxes you will actually buy.
Formula
There are 144 square inches in a square foot (12 × 12).
Worked example
A 12 × 10 ft kitchen floor with 12 × 12 in tiles, 10% waste and 10 tiles per box.
- Area: 12 × 10 = 120 ft².
- Tile area: 12 × 12 ÷ 144 = 1 ft².
- Tiles: 120 ÷ 1 × 1.10 = 132 tiles.
- Boxes: 132 ÷ 10 = 13.2 → 14 boxes (140 tiles).
- At $3.50 per ft², 140 ft² of tile costs $490.
Tiles per square foot by common size
| Tile size | Tiles per ft² | ft² per tile |
|---|---|---|
| 3 × 6 in (subway) | 8 | 0.125 |
| 4 × 4 in | 9 | 0.111 |
| 6 × 6 in | 4 | 0.25 |
| 12 × 12 in | 1 | 1 |
| 12 × 24 in | 0.5 | 2 |
| 24 × 24 in | 0.25 | 4 |
Based on face size, ignoring grout joints.
Caveats and assumptions
- Grout joints are ignored, so the count is slightly high — useful as spare tiles for future repairs.
- Large-format tiles waste more on cuts in small rooms; consider 15% or more.
- Buy all boxes from the same lot or batch number to avoid colour variation.
- Subtract large permanent obstacles (kitchen islands, tubs) from the area, but not small ones like toilets.
Frequently asked questions
How much extra tile should I buy?
Common practice is about 10% extra for a straight layout and about 15% for diagonal, herringbone or other patterns with many cuts.
How many 12×24 tiles are in a square foot?
One 12 × 24 in tile covers 2 ft², so there are 0.5 tiles per square foot. A 100 ft² room needs 50 tiles before waste, about 55 with 10%.
How do I calculate tile for a wall?
Use the wall's width and height as length and width, subtract windows and doors, and add 10–15% waste.
How many subway tiles do I need for a backsplash?
Standard 3 × 6 in subway tiles cover 0.125 ft² each, so 8 per square foot. A 30 ft² backsplash needs 240 tiles before waste.
Does grout spacing change the number of tiles?
Slightly. Grout joints make each tile cover a little more area, reducing the count by a few percent. This calculator ignores them for a safety margin.
Sources
- NIST — Unit Conversion — inch, foot and centimetre definitions
- Tile Council of North America (TCNA) — industry installation standards and handbook
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.