Tile Calculator

How to use the tile calculator

Measure the surface you are tiling — floor, shower wall, or backsplash — and enter its length and width in feet. For walls, length is simply the wall’s width and width is its height; the multiplication does not care which is which. Irregular spaces break into rectangles: an L-shaped bathroom floor is two runs of this calculator added together.

A backsplash interrupted by a window is best treated as the full rectangle, with the cutout absorbed into your waste allowance, because the tiles you cut around a window opening generally cannot be reused anywhere else, and deducting the opening tends to leave you short rather than efficient.

Pick the tile size from the presets or choose Custom and type the dimensions in inches off the box label. Size changes the count dramatically, and not in proportion to what it looks like: the same 88 square feet of order area is 88 twelve-inch tiles but 352 six-inch tiles, because halving each dimension quarters the area of the tile.

That matters for far more than the tile budget — it multiplies the grout you mix, the spacers you buy, the linear feet of joint you have to clean, and the hours you spend on your knees. Plank formats such as 12 by 24 are entered exactly as labelled, and orientation makes no difference to the area.

If you know how many tiles come in a box, add it under Advanced and the tool returns a box count rounded up to whole cartons. Like flooring, tile is dye-lotted, so buy every box from the same lot number and check each one at pickup: a lot mismatch shows up as a visible shade band across the finished surface and cannot be fixed afterwards.

Buy the full order before the first tile goes down and keep the leftovers — a cracked tile five years from now is a twenty-minute repair when three spares are in the garage and a sourcing nightmare when they are not. Remember too that this counts tile only: mortar, grout, backer board, waterproofing, and trim pieces are separate, and a large or wet-area installation deserves a professional takeoff rather than ours.

How much spare tile should you order?

Waste matters more with tile than with almost any other material, because every cut piece at a wall edge is usually unusable on the opposite side, and tile also breaks — in shipping, in cutting, and occasionally in your hands.

Ten percent is the standard allowance for straight layouts and it is what manufacturers advise: Daltile recommends buying roughly ten percent more than you expect to need, so that the leftovers are attic stock from the same dye lot and printing run. Move to fifteen percent for diagonal layouts and herringbone, for large-format tile in small rooms where cuts dominate the area, and for natural stone, which chips more readily and varies more in shade than porcelain does.

The formula, worked line by line

Tile math is one area divided by another: the area you are covering, inflated by a waste allowance, divided by the area of a single tile. The only conversion involved is turning tile dimensions in inches into square feet, which means dividing by 144 rather than by 12, because you are converting an area and not a length. That single detail is the most common arithmetic mistake people make when they try this on paper.

Everything after that is division and rounding up. Tiles round up because you cannot buy four-fifths of a tile, and boxes round up for the same reason. The waste percentage is the only judgement call in the whole calculation, and it is the one worth thinking about for a minute, because it is the difference between finishing the job and driving back to a store that has moved on to a different dye lot.

tile area sq ft = (tile width in × tile height in) ÷ 144
order area = length ft × width ft × (1 + waste% ÷ 100)
tiles = order area ÷ tile area, rounded UP to a whole tile
boxes = tiles ÷ tiles per box, rounded UP to a whole box

The estimate deliberately ignores grout joints. In reality each tile occupies slightly more floor than its own face: a 12-inch tile set with a quarter-inch joint takes up 12.25 inches of floor, so it covers about 4 percent more area than the raw arithmetic credits it with, and about 2 percent more with an eighth-inch joint.

That works in your favour as a small extra buffer on top of the waste allowance. Do not try to claw it back by trimming the order — the saving is a tile or two, and the downside is a shade-mismatched repair.

Two things the tile count does not decide for you. Mortar and grout are separate purchases sized off coverage figures on their own bags, and both change with tile size and joint width.

And large-format tile carries requirements the count cannot express: American Olean specifies medium-bed mortar for tiles over 20 by 20 inches, at least 90 percent mortar contact behind the tile, and a minimum grout joint of 3/16 inch. Read your own manufacturer’s installation sheet before you commit to a big-format layout, and treat this page as a shopping estimate rather than an installer’s takeoff.

Questions people ask