Tile Calculator

The tile-plus-joint footprint

Every tile estimate on this page is one division: the area you want covered, divided by the floor that one installed tile accounts for. The subtlety is in the second number. A tile does not occupy only its own face. It also claims half of the grout joint along each of its four edges, and half a joint on each side adds up to one full joint width in each direction. So the engine treats each tile as a cell of (tile width + gap) × (tile height + gap) square inches and divides by 144 — that is 12 × 12, plain arithmetic on the definition of the foot — to get the square feet each tile covers.

For the worked bathroom floor: a 12 × 12 in tile with a ¼ in joint is really a 12.25 × 12.25 in cell, which is 1.0421 sq ft. Divide 100 sq ft by that and the floor needs 95.96 tiles net — against exactly 100 if the same tiles were butt-jointed with no gap at all. Adding the 10% waste convention lifts the requirement to 105.56 tiles, which rounds up to 106 whole tiles, or 11 boxes of 10 with 4.44 tiles spare. Every one of those figures was produced at build time by the same tileEstimate function the form above runs in your browser, so this copy cannot disagree with the tool.

The five stages, in order

1. Geometry. The area to tile is yours to supply, in square feet or square metres. This tool does not derive it from room dimensions — the square footage calculator does that, summing any number of rectangles — because tiled areas are rarely one clean rectangle, and the tub, island, or vanity the tile stops at is a deduction only you can see. Whatever you enter is taken as the finished tiled surface.
2. Coverage. The per-unit coverage is the tile-plus-joint footprint above. On most tools on this site the coverage figure is a manufacturer or industry constant kept in the site's materials data file with its source; tile is deliberately different. Tile sizes are not standardised across products, so that file holds no tile constant at all — it records tile size as a user input — and the footprint is derived entirely from the dimensions you type. Nothing here is cited because nothing here is sourced: it is your tile, measured.
3. Waste. The net tile count is multiplied by (1 + waste% ÷ 100). The prefilled 10% is a trade convention, not a manufacturer figure — the materials data file labels it the widely used starting point for flooring, tile, and drywall — and it is adjustable in the form. What the percentage should be for your layout is the subject of the site's guide Waste factors, explained; this page only applies the number you choose.
4. Package rounding. The waste-adjusted count is rounded up — first to whole tiles and then, if you entered tiles per box, to whole boxes: ceil(adjusted tiles ÷ tiles per box). This is the only rounding anywhere in the chain; everything before it is carried at full precision. An exact fit does not buy a phantom box, either: the rounding tolerates a floating-point sliver of one part in a billion, so the 110 tiles of the exact-fit example with waste become 11 boxes of 10, not 12.
5. User-priced cost. If you enter a price per box, the cost line is boxes × that price. The site never supplies, averages, or suggests a tile price; the field is blank until you fill it, and the cost line does not appear without both a box size and a price.

Why each input matters

Area is the biggest lever and a linear one: double the area and every figure downstream doubles before rounding. It is also the input most often entered in the wrong unit, which is covered under misreadings below.

Tile width and height go in as inches (centimetres in metric mode). Both edges matter for rectangular tile, and the order does not: a 12 × 24 plank and a 24 × 12 plank produce the same footprint because the two sums are simply multiplied. The engine accepts edges up to 120 in; anything larger is rejected as out of range rather than silently estimated.

Grout gap is the input with the counter-intuitive sign: a wider joint means fewer tiles, because each tile's cell grows. How much fewer depends on the joint's size relative to the tile edge, not on the joint alone. The ¼ in joint on the 12 in bathroom tile trims the net count by 4%; the ⅛ in joint on the 2 in shower mosaic — half the width, on a tile a sixth the size — trims it by 11.4%. Leave the field blank or enter 0 for a butt joint. The engine caps the joint at 2 in.

Waste is a percentage of the tile count, applied once, before packaging. It is not a percentage of boxes and it is not re-applied to the spare tiles the rounding produces. Tiles per box changes nothing about how many tiles you need; it changes the granularity of the round-up and therefore the spare count, which is why a box of 2 large-format tiles leaves fewer spares than a box of 44 subway tiles for the same shortfall. Price per box only ever multiplies the box count.

Seven worked examples

Each row below was computed at build time by the tile engine from the inputs shown. Net tiles are the pure geometry; "with waste" applies the percentage in the waste column; the final column is what the result box would tell you to buy.

Kitchen floor, 12 × 24 in plank tile. A 180 sq ft floor in plank tile with a ⅛ in joint: each cell is 2.0314 sq ft, so the floor needs 88.61 tiles net and 97.47 with 10% waste. Boxes of 8 round that to 13 boxes with 6.53 tiles spare. This example also has a value in the price field — a stand-in of $30 per box that represents whatever your supplier quotes, not a price of anything — so the cost line reads 13 × $30 = $390. Change the price and only that last line moves.

Shower floor, 2 × 2 in mosaic. Counted as loose tiles, a 40 sq ft shower floor in 2 in mosaic with a ⅛ in joint needs 1,275.57 tiles net against 1,440 butt-jointed — the joint does real work at this scale. With waste, 1,404 tiles. In practice you would buy mosaics by the sheet; enter the sheet's overall size as the "tile" instead, and the same arithmetic counts sheets (see the FAQ).

Backsplash, 3 × 6 in subway tile. A 48 sq ft backsplash with a 1/16 in joint: 0.1289 sq ft per cell, 372.29 tiles net, 409.51 with waste, and boxes of 44 round that to 10 boxes with 30.49 tiles spare. Note how large the spare figure is relative to the shortfall: a big carton rounds coarsely.

Open-plan floor, 24 × 48 in large format. A 350 sq ft floor with a 3/16 in joint and the 15% waste the FAQ suggests for large-format tile: each cell is 8.094 sq ft, so 43.24 tiles net becomes 49.73 with waste and 25 boxes of 2, 0.27 tiles spare. Here the waste percentage moves the order by far more than the joint does.

Metric floor, 60 × 60 cm. In metric mode the form takes 15 m², a 60 cm tile, and a 3 mm joint, and converts them exactly: the area becomes 161.46 sq ft, each edge 23.622 in, and the joint 0.1181 in. The engine then runs unchanged. Each cell is 0.3636 m² (3.9139 sq ft), the floor needs 41.25 tiles net and 45.38 with 10% waste, and boxes of 4 round that to 12 boxes with 2.62 tiles spare. The footprint line in the result box reads in m² when metric is selected; the counts are identical in either unit system.

Exact fit, 12 × 12 in butt-jointed. With no joint and no waste, 100 sq ft of 12 in tile is exactly 100 tiles and exactly 10 boxes of 10 with 0 spare — the round-up adds nothing when nothing is owed. Put the default waste back and the same floor wants 110 tiles, which is 11 boxes: one more box for the margin, none for rounding noise.

Reading the result box

The headline line is the purchase: Buy N boxes when you entered tiles per box, Buy N tiles when you did not. Beneath it, Each installed tile occupies is the footprint from stage two, in sq ft or m² according to the unit toggle. Tiles needed shows the net count and the waste-adjusted count side by side, so you can see how much of the order is margin. The last line, In whole boxes or Rounded up, repeats the purchase and adds the spare count. Spare is purchased minus needed-with-waste: it is what rounding forced you to buy beyond the allowance, and it is not itself the waste allowance. The copy button puts a one-line summary — tiles including waste and the purchase — on the clipboard for a shopping list.

Common misreadings

Tile size typed in feet. The tile fields take inches. Enter the bathroom's 12 in tile as 1 × 1 — thinking in feet — and the engine obediently prices a floor of one-inch tiles: 10,138 of them, about 95.6 times the correct 106. If the count looks absurd, check the tile fields first. This is the tile counterpart of the inches-versus-feet thickness error on the concrete pages.

A millimetre joint typed into the inch field. In imperial mode the joint is inches; in metric mode it is millimetres. Type a 1 mm joint as "1" with imperial selected and it becomes a one-inch joint, dropping the bathroom order from 106 to 94 tiles. Larger slips are caught — the engine rejects joints over 2 in — but a small one passes as a plausible joint.

Area in the wrong unit. Square inches in the square-foot field, or square metres with imperial selected, scale the whole order. The area is not sanity-checked against the tile size, because a very large or very small area is perfectly legitimate; the toggle is the only guard.

Sheets and tiles mixed. Entering an individual mosaic face but sheets per box (or the reverse) produces a box count that means nothing. Pick one unit for the tile fields and the box field and stay with it.

Waste counted twice. The order already includes the waste percentage; adding "a box for waste" on top of it compounds the margin, which is exactly what the engine's waste-before-packaging order prevents. If you want a larger cushion, raise the percentage rather than the box count, so the spare figure stays honest.

Where the model stops

This is a count of field tile and nothing else. It does not count trim, bullnose, cove base, edge profiles, or border and accent pieces — those are linear items to take off your drawing, and the linear feet calculator totals the runs. It does not estimate thinset or mortar, grout, backer board, membrane, spacers, or sealer; each of those is a separate purchase with its own coverage figure, and this site holds no such figure for tile products. Waste is one flat percentage: the engine has no knowledge of diagonal sets, offsets, herringbone, pattern repeats, or which offcuts can be reused, which is why the waste guide exists. Nothing is deducted from the area you enter, and sheet-mounted mosaics are treated as loose rectangles. As the note under the form says, tile counts here are purchasing math only: substrate flatness, waterproofing, movement joints, whether a surface is suitable for tile, and any structural or permit question are for a licensed professional — this page estimates quantities and makes no other determination.

Related tools and guides

Get the area first with the square footage calculator, which adds up any number of rectangles. If your carton is labelled in square feet of coverage rather than a tile count, the flooring calculator takes box coverage directly and runs the same waste-then-boxes pipeline. The paver calculator counts pavers by the same per-piece footprint and adds the sand bedding beneath them, and the construction unit converter moves any figure between imperial and metric. For the reasoning behind the percentages, start with Waste factors, explained and the rest of the guides.

Frequently asked questions

Calculations never leave your browser. The full estimation pipeline — and why waste precedes packaging — is on the methodology page.