How the tile calculator counts tiles
Each tile covers its own face plus half a grout joint on every side, so the area one tile occupies is (length + joint) × (width + joint). Divide the floor's square footage by that, then add your allowance for cut pieces. A square foot is 144 square inches, which is why the formula divides by 144.[1]
Worked example: a 120 sq ft floor (10 × 12 ft) in 12 × 24 in tiles with ⅛ in joints and a 10% allowance for cuts.
Coverage per tile (sq ft) = (L + j) × (W + j) ÷ 144(12 + 0.125) × (24 + 0.125) ÷ 144 = 2.0314 sq ft
Tiles = area ÷ coverage per tile × (1 + allowance)120 ÷ 2.0314 = 59.1; × 1.10 = 65.0 → 65 tiles
Ignoring the joint slightly overstates the tiles you need; ignoring cuts understates it far more. If you do not know the floor's area yet, measure it room by room with the square footage calculator.
Tiles per 100 square feet by tile size
Bigger tiles mean fewer pieces: 100 sq ft takes 98 tiles of 12 × 12 in but only 25 of 24 × 24 in, before cuts. With ⅛ in joints:
| Tile (inches) | Covers per tile (sq ft) | No allowance | With 10% allowance | With 15% allowance |
|---|---|---|---|---|
| Subway 3 × 6 | 0.133 | 753 | 828 | 866 |
| Plank 6 × 24 | 1.026 | 98 | 108 | 113 |
| 12 × 12 | 1.021 | 98 | 108 | 113 |
| 12 × 24 | 2.031 | 50 | 55 | 57 |
| 18 × 18 | 2.281 | 44 | 49 | 51 |
| 24 × 24 | 4.042 | 25 | 28 | 29 |
How much extra tile to buy
How much extra tile to buy depends on the layout and the room, and no national standard sets a percentage, so the calculator treats it as your allowance. The 10% default is only a starting value. Raise it when the job has many cuts: diagonal or herringbone patterns, small rooms with lots of edges, large-format tile that breaks expensively, or a pattern that must match. Lower it for a big rectangular room in a small tile.
| Allowance | Tiles | Square feet to buy |
|---|---|---|
| 0% | 60 | 120.0 |
| 5% | 63 | 126.0 |
| 10% | 65 | 132.0 |
| 15% | 68 | 138.0 |
| 20% | 71 | 144.0 |
Keep a few spare tiles after the job: dye lots change, and a matching replacement can be hard to find years later.
Boxes, not tilesTile is sold by the box, and boxes list the square feet they cover. Enter that figure and the calculator rounds up to whole boxes; enter your price per square foot to see the cost. The grout for the same floor comes from the grout calculator.
Floor tile calculator vs. wall tile: showers and backsplashes
The same math works on walls: use the wall's width and the height you will tile instead of length and width, and subtract windows and doors. For a shower, add the area of each wall separately. A tub surround with two 5 ft walls and one 2.5 ft end wall tiled 6 ft high is (5 + 5 + 2.5) × 6 = 75 sq ft. Tile and labor are often the biggest lines in a bath budget; the bathroom remodel cost calculator works out floor and wall tile areas from the room's size.
What tile projects cost
Tile prices vary too much by material and region to quote here, so enter your own price per square foot. For scale, the Census Bureau's 2023 American Housing Survey put the median owner-occupied flooring, carpeting or ceiling job at $3,000 (average $4,829), and the median bathroom remodel at $5,000 (average $9,322), across 10.9 million and 7.5 million jobs in two years.[2] Those medians cover every kind of job, from a single room to a whole house. If you borrow against your home for a tile job, the IRS lets you deduct the interest only when the money substantially improves the home, which a remodel can and a repair does not,[4] and the CFPB points out that a line of credit usually has a variable rate, so its payment can change.[5] If you are financing a larger remodel, the home improvement loan calculator compares the payments.
Tile square footage calculator vs. home square footage
The area you tile is the floor you can see, measured inside the walls, and it is not the same as a home's official square footage. Appraisals for Fannie Mae measure finished area under the ANSI Z765-2021 standard and report below-grade levels separately,[3] so don't take a listing's square footage as the amount of tile to buy.
Frequently asked questions
How many tiles do I need for 100 square feet?
With ⅛ in grout joints: about 98 tiles of 12 × 12 in, 50 of 12 × 24 in or 25 of 24 × 24 in before cuts. Add your allowance for cuts and breakage on top.
How do I calculate how much tile I need?
Find the area in square feet, divide it by the area one tile covers including its grout joint, add an allowance for cuts, and round up to whole boxes.
How much extra tile should I buy?
There is no fixed standard; it depends on the layout. Straight layouts in large rooms need the least extra, while diagonal or herringbone patterns, small rooms and large-format tile need more. Compare a few allowances in the calculator.
Does grout spacing change how many tiles I need?
Slightly. A wider joint makes each tile cover a little more floor, so you need fewer tiles: 100 sq ft of 12 × 12 in tile takes 100 tiles with no joint and 98 with ⅛ in joints.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically (Special Publication 811)
- American Housing Survey 2023, Table C-16-OO: Home Improvement Costs, Owner-Occupied Units
- B4-1.3-05, Improvements Section of the Appraisal Report (ANSI Z765-2021 square footage) (Selling Guide)
- Publication 936 (2025), Home Mortgage Interest Deduction
- What is the difference between a home equity loan and a home equity line of credit (HELOC)?