Tile and Flooring Calculator
Tiles, boxes and attic stock for a room, with a waste allowance sized to the lay pattern.
Tile & Flooring Calculator
How many tiles, how many boxes, and how much spare to keep. The spare is the part that matters: a discontinued run you cannot match is a whole-floor problem, not a repair.
Quick answer: tiles per square foot
| Tile | Per ft² | 12 × 10 ft room, +15 % |
|---|---|---|
| 12 × 12 in | 1 | 138 |
| 12 × 24 in | 0.5 | 69 |
| 18 × 18 in | 0.444 | 62 |
| 24 × 24 in | 0.25 | 35 |
| 24 × 48 in | 0.125 | 18 |
Nominal tile size, joints not counted. 15 % covers a typical lay with some cuts; keep at least one box from the same production run as spare, because a discontinued run cannot be matched later.
| Floor area | — |
|---|---|
| Area per tile | — |
| Tiles, no waste | — |
| Tiles with waste | — |
| Boxes to buy | — |
| Left over after the job | — |
Waste and attic stock are two allowances, not one. Waste is spent on the job; attic stock leaves with the owner. Daltile's FAQ lists them separately: take wastage into account, and then "purchase approximately 10% more tile than you anticipate needing". That extra sits on top of the cut allowance, not inside it. The University of Arizona's tile standard sizes the spare at "one (1) box or at minimum, 2 percent" and requires it "from same production run or batch". Buy the spare with the order. A box bought later comes from a different run.
The window for matching is about six months. Daltile can sometimes still find a discontinued line inside six months; "[b]eyond six months, it becomes extremely difficult". Shade is the easy half. The other is caliber, the facial-dimension band a run was sorted into. Marazzi: mixed calibers "result in a variation in grout joint widths, exaggerated as the size of the tile increases". ANSI A108.02 §4.3.8 sizes the joint to the tile, "at least three times the actual variation of the facial dimensions of the tile supplied", so 1/16″ of variation forces a 3/16″ joint, and none is allowed under 1/16″. A joint grouted to one run's variation has no slack for another's.
The waste percentages are rules of thumb. American Olean's nine-page Tile Pattern Guide gives piece counts "For 100 Square Feet" for every pattern and no waste figure, and its instruction to "square off from the center" puts a cut course on both walls, not one. Cuts follow the perimeter, not the area. A 12 × 10 ft room in 12 × 24, the 24″ edge along the 12′ wall, divides exactly: 60 tiles, no cuts. Lengthen it an inch and the seventh course is a 1″ sliver, so centred the field is five full courses and two 12-1/2″ borders. Seven columns, and the 11-1/2″ offcuts are too narrow to use opposite. 70 tiles placed against 61 by area. 15% buys exactly 70.
What I check on a job
Before the box count goes out. Before I trust the box count, I replace the tiles per box with the figure on the product's own data sheet. Tiles per box varies by product and size, and the 8 in the field is only the default. The calculator assumes one rectangle, but a real floor is a room plus a closet, a hall return and a run to the threshold. I run each piece as its own rectangle and add the results, but that does not account for the extra cuts. The tool works from area alone, and every added piece adds perimeter that only the waste allowance pays for. So a floor in pieces is not the "simple room" of the 10% setting; I use 15% for some cuts, or 20% where the obstructions pile up. In practice the number goes wrong at delivery, not in the arithmetic. Before any carton is opened or a tile is set, I confirm that the whole order, spare included, arrived as one production run.
Tile counts assume a rectangular room and a straight lay; the waste allowance is what covers perimeter cuts, breakage and pattern loss. Boxes are always rounded up, because you cannot buy part of a box, and the rounding is usually where the attic stock comes from for free.
Worked example
A 12 × 10 ft room in 12 × 24 in tile, 8 to a box: how many boxes?
- Area = 120 ft²; a 12 × 24 tile covers 2 ft², so 60 tiles bare.
- 15% waste for a typical lay: 69 tiles.
- Boxes of 8: ceil(69 ÷ 8) = 9, plus one box of attic stock = 10.
10 boxes (80 tiles) including one spare box; 9 boxes with no attic stock. A diagonal lay moves the waste to 20% and the count with it.
8 values on this page were driven in a browser and compared with independently derived figures on 2026-10-29 (2808 values across 228 calculators site-wide).
Questions
How much waste for tile?
10% for a straight lay, 15% typical, 20% for a diagonal lay, 25% for herringbone. The pattern decides it, not the room.
What is attic stock?
A spare box kept back for repairs, from the same dye lot. The calculator adds it as a whole box because a matching tile is hard to buy later.
How many 12 × 24 tiles does a 12 × 10 ft room take?
Exactly 60 if the 24 in. edge runs along the 12 ft wall: it divides with no cuts. Lengthen the room an inch and, centred, it becomes five full courses and two 12-1/2 in. borders: 70 tiles placed against 61 by area. A 15% allowance buys exactly 70. Cuts follow the perimeter, not the area.
Why can't tile from two runs be mixed?
Shade, and caliber: each run is sorted into a band of real face size. ANSI A108.02 §4.3.8 sizes the joint at three times the tile's variation, so 1/16 in. of variation forces a 3/16 in. joint. A joint grouted to one run's variation has no slack for another's.