Tile Calculator
Work out how many tiles and boxes a floor or wall needs, including the waste allowance your layout demands and what the whole job costs per square foot.
Length × width; split L-shaped rooms into rectangles.
Printed on the carton, next to the square footage.
Diagonal and herringbone cut more tiles at the walls, so they carry a bigger allowance.
Ordering includes a 10.0% allowance for cuts and breakage. Buy every box in one go — tile is made in dye lots and a later box can be a visibly different shade.
What this calculator does
Tile is one of the few materials where ordering the exact measured amount guarantees a problem. Every job cuts tiles at the walls, a few arrive cracked inside the carton, and one always breaks on the wet saw at the worst moment. Order precisely and you make a second trip — which, because of dye lots, may mean a visibly different tile.
This calculator converts your area into a tile count, applies the waste allowance your layout actually needs, rounds up to whole boxes because that is the only way tile is sold, and prices the result per square foot so you can compare options honestly.
The arithmetic
Three steps, and the first is the one people get wrong.
Find the coverage of one tile. Tile is sized in inches, rooms are measured in feet, and there are 144 square inches to the square foot:
12 × 24 in tile → (12 × 24) ÷ 144 = 2 sq ftDivide the area by that number. A 120 square foot floor needs 60 of those tiles to cover the bare area.
Add the waste allowance and round up to boxes. At a straight layout that is 66 tiles. In boxes of eight, that is nine boxes — 72 tiles — leaving six spares.
The final number is always boxes, never tiles, because suppliers do not break cartons.
Why the layout changes the number
The waste allowance is not a superstition, it is geometry. In a straight layout only the tiles meeting a wall get cut, and the offcut from one side often serves the other. Turn the grid 45 degrees and every tile along every wall becomes a triangle, and the offcuts rarely fit anywhere else. Herringbone cuts at both ends of every course.
| Layout | Allowance | Why |
|---|---|---|
| Straight | 10% | Cuts only at walls, offcuts often reusable |
| Diagonal | 15% | Every perimeter tile cut on the bias, offcuts wasted |
| Herringbone | 20% | Cuts at both ends of every run |
Two other things push the allowance up. A room with many corners, alcoves or doorways cuts more tile than a plain rectangle of the same area. And large-format tile — anything over 15 inches on a side — wastes more per cut, simply because each mistake destroys more coverage.
What drives the cost
The per-square-foot figure in the results is the honest comparison number, and it is usually higher than the shelf price implies, because you pay for whole boxes and for the waste allowance. A $38 box covering 16 square feet looks like $2.38 a square foot; after a 10% allowance and box rounding it is closer to $2.85.
That gap matters when comparing a cheap tile in an awkward size against a slightly dearer one that divides neatly into your room.
What this leaves out
The tile is rarely the largest line on a tiling invoice. This calculator deliberately estimates tile only, so be clear about what you still need to budget:
- Thinset mortar, roughly one 50 lb bag per 40–60 square feet depending on trowel size and tile format.
- Grout, which varies enormously with joint width and tile size — a 1/16 in joint on large tile uses a fraction of what 1/4 in joints on mosaic do.
- Backer board or uncoupling membrane, plus the screws and tape.
- Trim pieces — bullnose, pencil liners, Schluter edging — sold by the piece and easy to forget until the last day.
- Labour, which on tile is commonly two to three times the material cost.
It also assumes a flat, square room. If your walls are out of parallel — normal in older US housing stock — the cut tiles taper and waste rises. Measure the room at both ends before trusting a single width.
Getting the measurement right
Measure in feet to one decimal place, and treat each rectangle separately in an L-shaped room rather than trying to average it. For a wall, measure floor to ceiling and along the run; for a backsplash, measure counter to cabinet.
If the layout is undecided, price both. Running the numbers for straight and herringbone takes ten seconds here and occasionally changes the decision, because the pattern that costs 20% more in tile may also need a more expensive trim.
For related projects, the flooring calculator handles plank and sheet goods sold by the carton, the paint calculator covers the walls above the tile, and if you are tiling over a new slab the concrete calculator sizes the pour. The guide on how much paint a room needs explains the same measure-then-divide-by-coverage logic in more depth.
How this is calculated
tile area (sq ft) = (tile width in × tile length in) ÷ 144 tiles for area = area to tile ÷ tile area tiles to buy = tiles for area × (1 + waste allowance) boxes = ceiling(tiles to buy ÷ tiles per box) Waste allowance: 10% straight, 15% diagonal, 20% herringbone.
Frequently asked questions
- How much extra tile should I buy?
- Ten percent over the measured area for a straight layout, fifteen for a diagonal run and twenty for herringbone. The allowance covers cuts at the walls, the occasional cracked tile and the few that arrive chipped. Diagonal and herringbone patterns cut a triangle off far more tiles, which is why they need more.
- Why does the box say a square footage instead of a tile count?
- Because tile is sold by coverage, not by piece. A box of 12×24 in tiles holding eight pieces covers 16 square feet. Our calculator asks for tiles per box so it can round up to whole boxes, since no supplier will sell you three tiles out of a carton.
- Do I need to subtract cabinets or fixtures?
- Subtract anything larger than about 10 square feet, such as a kitchen island footprint or a bathtub. Do not bother deducting a toilet flange or a narrow closet — the tile you save is less than the tile lost to the extra cuts those obstacles create.
- What is a dye lot and why does it matter?
- Tile is fired in batches and colour varies slightly between them. The lot number is printed on the carton. Buy every box for a job at once and check the numbers match, because a box bought a month later can be visibly different under the same light.
- Should I keep the leftover tiles?
- Yes. Store a full box flat somewhere dry. Tile lines are discontinued constantly, and a single cracked tile three years from now is unrepairable without a match. The spares are the cheapest insurance in the whole project.