To count tiles, multiply the area in square feet by 144 and divide by the size of one tile in square inches, then add 10% to 15% for cuts and breakage. A 12 × 10 ft floor in 12 × 12 in tile needs 120 tiles, or 135 with 12% waste. That same floor takes about 2 bags of thinset and 2 bags of grout.
Work in square inches, because that's how tiles are sized.
Tiles = floor area in sq ft × 144 ÷ area of one tile in sq in
Then add a waste allowance and round up. For a 12 × 10 ft bathroom floor with 12 × 12 in tile:
That's exactly what our tile calculator gives for its default room. It also works out thinset, grout and cost from the same inputs.
One quirk works in your favor. The formula uses the tile's face size and ignores the grout joints. With a 3/16 in joint, each 12 in tile really takes up about 12.19 × 12.19 in of floor, so the true count is about 3% lower. Leave that as a small hidden cushion on top of your waste allowance.
This is the fastest way to sanity-check a quote or a shopping list. Multiply by your room's area in hundreds of square feet.
| Tile size | Area of one tile | Tiles per 100 sq ft | With 10% waste | With 15% waste |
|---|---|---|---|---|
| 3 × 6 in (subway) | 18 sq in | 800 | 880 | 920 |
| 4.25 × 4.25 in | 18.06 sq in | 798 | 877 | 917 |
| 6 × 6 in | 36 sq in | 400 | 440 | 460 |
| 12 × 12 in | 144 sq in | 100 | 110 | 115 |
| 12 × 24 in | 288 sq in | 50 | 55 | 58 |
| 18 × 18 in | 324 sq in | 44.4 | 49 | 52 |
| 24 × 24 in | 576 sq in | 25 | 28 | 29 |
A 30 sq ft kitchen backsplash in 3 × 6 subway tile is 30 × 144 ÷ 18 = 240 tiles, or 264 with 10% extra. Small tiles mean hundreds of pieces, which is why mosaics and subway tile are usually sold by the square foot or the sheet rather than counted one by one.
Every cut along a wall, around a toilet flange or at a door jamb turns part of a tile into scrap. A few will crack or arrive chipped. The waste percentage covers all of that.
| Layout | Typical waste allowance | Why |
|---|---|---|
| Straight lay, large simple room | 10% | Cuts only at the edges |
| Straight lay, small room or lots of obstacles | 12% to 15% | Edge cuts are a bigger share of a small floor |
| Offset / brick pattern | 10% to 15% | Staggered rows leave more offcuts at the ends |
| Diagonal | 15% | Every edge tile is cut on an angle |
| Herringbone or chevron | 15% to 20% | Many small angled cuts, and mistakes are costly |
These are common rules of thumb, not a standard. The calculator defaults to 12%, which suits a typical straight-lay bathroom. Bump it up for patterns or if it's your first tile job.
Buy it all at once. Tile is made in production runs, and the color, shade and even the exact size can vary between them. Check that every box shows the same lot number, and keep at least one full box after the job. If a tile cracks in five years, you'll want a perfect match, and that style may be long gone.
Divide the square footage you're buying by the coverage printed on the box. Box sizes vary a lot by tile and brand, so read the label. The calculator's box count assumes 10 sq ft per box, which is a reasonable placeholder for 12 × 12 tile. For the example room, 135 tiles of 1 sq ft each is 135 sq ft, or 14 boxes at 10 sq ft.
If your box says 15.5 sq ft, it's 135 ÷ 15.5 = 8.7, so 9 boxes. Always round up. Most stores take back unopened boxes, but check the return policy before you over-buy on special-order tile.
Pick a tile size and joint width, set your waste and price, and get tiles, boxes, bags and cost. Free, no signup.
Open the Tile Calculator →Grout fills the joints, so it depends on two things: how wide the joints are, and how many of them there are. Smaller tiles have far more joint per square foot. Here's how far one 25 lb bag of sanded grout goes in the calculator's model, which is calibrated to typical manufacturer charts for standard-thickness floor tile.
| Tile size | ⅛ in joint | 3/16 in joint | ¼ in joint | ⅜ in joint |
|---|---|---|---|---|
| 6 × 6 in | 87 sq ft | 59 sq ft | 44 sq ft | 30 sq ft |
| 12 × 12 in | 172 sq ft | 115 sq ft | 87 sq ft | 59 sq ft |
| 18 × 18 in | 257 sq ft | 172 sq ft | 129 sq ft | 87 sq ft |
| 24 × 24 in | 342 sq ft | 229 sq ft | 172 sq ft | 115 sq ft |
Thicker tile has deeper joints and uses more grout, so treat these as a starting point and check the chart on the bag you buy. Grout is cheap next to tile. Running short halfway through a floor is the expensive mistake, because a second batch can dry a slightly different color.
Thinset coverage depends on the trowel notch, and the notch depends on the tile size. Bigger tiles need a bigger notch and more mortar to fill the gap under them. The calculator plans on about 95 sq ft per 50 lb bag for tiles under 12 in, 75 sq ft for 12 to 17 in tile and 65 sq ft for 18 in and up. For the 120 sq ft example, that's 2 bags.
The industry standard, ANSI A108, calls for at least 80% mortar contact under tile in dry interior areas and 95% in wet areas like showers. The only way to know is to lift a freshly set tile now and then and look at the back.
Tiles with any side 15 in or longer count as large-format tile. They often need a large notch, back-buttering (a thin skim of mortar on the back of the tile) and a flatter floor than smaller tile. Follow the mortar maker's trowel chart rather than a rule of thumb.
At $4 per sq ft, the calculator's default, the 120 sq ft example comes to about $538 for tile once you include 12% waste. Budget on top for thinset, grout, backer board or an underlayment membrane, and tools like a trowel, spacers and a cutter.
If tile is just one part of the job, the bathroom remodel cost calculator puts it next to fixtures and labor. Tiling one room and putting planks in the next? The flooring calculator does box counts for laminate, vinyl plank and hardwood.
Multiply square feet by 144, divide by the tile's square inches, and add 10% for a straight lay or 15% for diagonal and herringbone. Buy every box from the same lot, keep one spare, and don't forget the grout and thinset.
100 tiles, since each 12 × 12 tile covers exactly 1 sq ft. Add waste on top: 110 tiles at 10% for a straight lay, or 115 at 15% for a diagonal layout.
Plan on 10% extra for a straight lay in a simple room, 12% to 15% for small rooms and offset patterns, 15% for diagonal and 15% to 20% for herringbone. Keep at least one spare box for future repairs.
The same way as a floor. Multiply the wall's width by the tiled height to get square feet, take off windows or other large openings, multiply by 144 and divide by the tile's area in square inches. A 30 sq ft backsplash in 3 × 6 subway tile takes 240 tiles, or 264 with 10% extra.
It depends on tile size and joint width. For 12 × 12 tile with a 3/16 in joint, one 25 lb bag covers about 115 sq ft, so 100 sq ft takes one bag. Small tiles with wide joints use much more: 6 × 6 tile with a ¼ in joint gets about 44 sq ft per bag.
Roughly one 50 lb bag per 95 sq ft for tile under 12 in, per 75 sq ft for 12 to 17 in tile and per 65 sq ft for larger tile. Larger notches use more, so check the trowel chart on the bag.