Tile Calculator — Tiles, Thinset and Grout
Enter the area and your tile size. You get the tile count with waste, plus the thinset and grout to go with it.
About the Tile Calculator
Tile waste is not padding — it is the offcuts around the edges, the one you drop, and the spares you will want in five years when a tile cracks and the line has been discontinued. Ten percent is the working minimum, and more if you are laying on a diagonal.
How to use it
- Enter the area to cover in square feet.
- Enter your tile dimensions in inches.
- Use 10% waste for a straight lay, 15% for diagonal or herringbone.
- Buy the full amount in one batch — dye lots vary noticeably between runs.
The formula
Tile area (sq ft) = (width × height) ÷ 144
Tiles = area × (1 + waste) ÷ tile area
The divide-by-144 converts square inches to square feet. A 12×12 tile is exactly 1 sq ft, which is why it remains the easiest size to estimate with.
Worked examples
| Area | Tile size | Each covers | Tiles +10% | Thinset bags |
|---|---|---|---|---|
| 100 sq ft | 12" × 12" | 1.000 sq ft | 110 | 2 |
| 100 sq ft | 18" × 18" | 2.250 sq ft | 49 | 2 |
| 100 sq ft | 3" × 6" subway | 0.125 sq ft | 880 | 2 |
| 40 sq ft | 24" × 12" | 2.000 sq ft | 22 | 1 |
The subway row shows why tile size drives labour more than material. Eight hundred and eighty small tiles is many times the work of 49 large-format ones over the identical area.
Common mistakes
- Buying tile in two batches. Dye lots differ. A second order weeks later can be visibly a different colour under the same light.
- Using 10% waste on a diagonal lay. Diagonal and herringbone patterns cut every perimeter tile. Fifteen percent is the realistic figure.
- Forgetting spares. Keep a box. Discontinued lines make a single cracked tile a room-wide problem years later.
- Under-buying thinset for large format. Big tiles need a deeper notch trowel and much more adhesive per square foot than the bag coverage suggests.
Terms explained
- Thinset
- Cement-based tile adhesive. One 50 lb bag covers roughly 95 sq ft with a ¼-inch notch trowel.
- Dye lot
- A production batch. Colour varies slightly between lots, so buy the whole job at once.
- Large format
- Any tile with a side over 15 inches. Needs a flatter substrate and more adhesive.
- Lippage
- When adjacent tile edges sit at different heights. Levelling clips largely prevent it.
Common questions
- How many 12x12 tiles do I need for 100 square feet?
- One hundred and ten, allowing 10% waste. A 12×12 tile covers exactly 1 square foot, which makes the maths simple.
- How much waste should I add for tile?
- Ten percent for a straight lay, 15% for diagonal or herringbone, and up to 20% for a room with many angles.
- How much thinset do I need?
- A 50 lb bag covers about 95 sq ft with a ¼-inch notch trowel. Large-format tile needs a bigger notch and covers less.
- How much grout do I need?
- Roughly 0.05 lb per square foot for standard joints. Wider joints and smaller tiles both increase it substantially.
- Should I buy extra tile?
- Yes — at least one full box. Lines get discontinued and dye lots shift, so replacing a single cracked tile later is often impossible.
- What size notch trowel should I use?
- A ¼-inch notch for tiles up to 12 inches, ½-inch for large format. The goal is full coverage on the back of the tile.
- Can I tile over existing tile?
- Sometimes, if the existing tile is sound and well bonded. It raises the floor height, which then affects doors and transitions.