EstimatorKitFree tile calculator
Tile in whole boxes, with the cuts counted
Give a room, a tile size, a joint width and a layout, and this returns the boxes to buy, the pieces that will be left over in the last one, and the bags of thinset for the trowel notch that tile needs. The joint is in the count rather than added afterwards, which matters most on small tile: 2 in mosaic at a 1/8 in joint holds 31.9 pieces to the square foot, not the 36 that dividing the areas gives.
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- 8 tile sizes
- 4 layouts
- 5 trowel notches
Wall tiling works the same way — give the wall height and its run instead of the two floor dimensions.
Grid square to the walls. Only the perimeter is cut, and each cut piece is cut once.
The default for 6 to 12 in floor tile on a flat slab. Roughly half a pound of thinset per square foot with a 1/4 in square-notch trowel, varying with trowel size and tile flatness.
Take this to the counter
12 boxes
- Tiles in those boxes
- 180
- Box covers
- 15 sq ft
- Thinset
- 2 × 50 lb
Where that box count came from
- 161 sq ft at 0.97 tiles per sq ft
- 156 tiles
- Straight lay, +10% cutting
- 172 tiles
- Spare left in the last box
- 8 tiles
The bare figure is the geometry and the padded figure is the order. Both are here so you can check a quote against one of them — straight lay, square room.
A 12 × 12 in tile with a 0.1875 in joint occupies 12.2 × 12.2 in of floor, so the grid holds 3.1% fewer tiles than dividing the room by the face size gives. On this tile that gap is the difference between a box over and a box short.
2 bags covers 161 sq ft at 100 sq ft per bag. Mortar is figured on the bare floor rather than the padded tile count, because the offcuts you set are still setting the same square feet.
How to work out how much tile to buy
Three inputs decide the order: the grid, the pattern and the notch.
Choose the tile, then set the joint you will actually space it at
Pick one of the eight prefilled sizes or type your own in inches. The joint field matters more than it looks: a tile occupies its face plus one joint, so 2 in mosaic at a 1/8 in joint fits 32 pieces into a square foot rather than 36. The pieces-per-box figure prefills from a common count and should be overwritten with the number printed on the end of the box in front of you.
Pick the layout, because that is what gets cut
A straight lay cuts the perimeter once. Running bond recovers the offcut into the next row but leaves a stub. A 45 degree diagonal turns every edge tile into a triangle and takes two cuts out of some corner pieces, and herringbone cuts both ends of the field as well as the sides. The allowance moves from 10 to 20 percent across those four, and the bare count sits next to the padded one so you can see which is which.
Set the trowel notch and read the mortar off the same area
The notch, not the tile, decides how far a 50 lb bag goes — 110 square feet from a 3/16 in V-notch, 28 from a 3/4 in U-notch. Choosing a size 15 in or larger switches the selection to a half-inch square notch and flags back-buttering, which is a second bed of mortar on the tile and adds roughly a third again to the bag count.
Technical specifications
| Tile sizes prefilled | 12×12, 12×24, 18×18, 24×24, 6×24 plank, 3×6 subway, 4 1/4 in wall, 2 in mosaic, plus any size typed in inches |
|---|---|
| Count basis | Grid pitch — tile face plus one joint — not area divided by face area |
| Joint widths accepted | 0 to 1 in, typed as a fraction: 1/16, 1/8, 3/16, 1/4 |
| Layout allowances | 10% straight lay, 12% running bond, 15% diagonal, 20% herringbone |
| Thinset coverage range | 110 sq ft per 50 lb bag at a 3/16 in V-notch down to 28 sq ft at a 3/4 in U-notch |
| Large-format threshold | 15 in on any edge, per ANSI A108.02 — switches the notch and flags back-buttering |
| Rounding | Up to whole boxes, with the spare pieces left in the last box reported separately |
| Works offline | Yes — the notch coverage and layout tables are compiled into the page, so it counts boxes in a basement with no bars |
Frequently asked questions
How many tiles are in a square foot?
Fewer than the face size suggests, and the gap is the joint. The grid a tile sits in is its own width plus one joint by its own length plus one joint, so 144 divided by that product is the honest figure: a 12 in tile at a 3/16 in joint gives 0.97 per square foot, a 3 by 6 in subway at 1/16 in gives 7.8, and a 2 in mosaic at 1/8 in loses four and a half pieces off the 36 that dividing areas promises. On anything 12 in and up the difference is around three percent and nobody notices; on mosaic it is eleven, which is a whole box.
How much extra tile should I buy?
The layout allowance covers the cuts, and one further full box covers the next ten years. Those are separate purchases for separate reasons: the allowance is consumed on the day, while the spare box is insurance against a cracked tile in 2031 when the line has been discontinued and the closest match is visibly not it. Boxes are the unit either way, so a job needing 11.2 boxes buys 12 for the floor and 13 to have a spare.
Why does a diagonal layout waste more tile than a straight lay?
Because a diagonal cut across a square tile produces two triangles and only one of them fits the wall it was cut for. In a straight lay the offcut from the left-hand edge is often exactly the piece the right-hand edge needs, so a careful setter recovers most of it; rotate the grid 45 degrees and the offcuts are triangles of a specific hand, and the mirror-image piece the other side of the room needs has to come out of a fresh tile. That is the whole of the five-point spread between the two allowances.
Is a waste percentage right for an odd-shaped room?
No, and it is worth knowing which way it is wrong. Cut waste happens at the perimeter, so it scales with the edge of the room while the tile count scales with the area — a 13 by 13 ft bathroom has 3.1 ft of wall for every 10 sq ft of floor and a 4 by 30 ft hallway has 5.7. The same ten percent that is generous in the square room is short in the hallway, and every doorway, column and alcove adds edge without adding floor. Push the allowance up by a few points for anything long, narrow or interrupted.
What size trowel notch does my tile need?
Big enough that lifting a set tile shows mortar on 80 percent of its back in a dry area, or 95 percent in a shower, on an exterior deck or under anything that gets wet — those two figures are the acceptance test in ANSI A108.5 and they are why the notch is on this page at all. In practice that means a 1/4 in square notch under 12 in tile on a flat slab, a half-inch square under large format, and a V-notch only under mosaic and small wall tile. Pull a tile up after the first few square feet and look; the coverage tells you more than the chart does.
What counts as large-format tile?
Any tile with one edge of 15 in or more, which is the threshold ANSI A108.02 uses. Crossing it changes three things at once: the substrate has to be flat to 1/8 in in 10 ft instead of 1/4 in in 10 ft, the mortar has to be a large-and-heavy-tile formulation that will not slump under the weight, and the offset in a running bond has to come down to a third of the tile length because a longer offset rides the crown that every long tile has and turns it into lippage.
Should I subtract the area under a kitchen island or a vanity?
Leave it in. Cabinets get replaced and islands get moved, and a floor that stops at the toe kick leaves a tile-shaped hole that no future owner can fill from the same lot. The exception is a genuinely permanent build — a masonry hearth, a tiled-in bath tub, a walk-in shower base with its own pan — where the floor tile physically cannot continue underneath and the deduction is real.
About counting tile, and the two numbers that move the order
A tile order is decided by the grid, not by the tile. What each piece actually occupies is its face plus one joint on two sides, so the count per square foot is 144 divided by that pitch, and the discrepancy against a plain area division grows as the tile shrinks. At 24 in it is about one percent and can be ignored. At 12 in it is around three. At 2 in mosaic it is eleven percent, and eleven percent of a shower floor is the difference between finishing and standing in a tile aisle on a Sunday holding an empty box. Any calculator that divides the room area by the tile area is quietly assuming a zero-width joint, which is a thing that exists only in rectified porcelain butted dry, and even then not really.
The second number is the cut, and it belongs to the pattern rather than to the tile. A straight lay produces offcuts that mostly find a home on the opposite wall, so the allowance is small. Turn the field 45 degrees and every perimeter piece becomes a triangle with a hand to it, the mirror image of which has to be cut from a fresh tile — hence the jump to fifteen percent. Herringbone cuts the ends of the field as well as the sides. What none of those percentages know is the shape of the room: waste is generated at the perimeter and tile is consumed by the area, so a long corridor eats a much higher fraction than a square bathroom of the same footage, and every doorway and column adds perimeter for free. Treat the figure as a floor to raise, not a ceiling. If the floor is going down in planks or sheet instead, the loss behaves differently again and the flooring calculator works in box coverage; carpet abandons percentages altogether because it is cut off a roll of fixed width.
Underneath the tile, the trowel is the variable and the standard is the check. ANSI A108.5 asks for mortar contact over 80 percent of the back of a tile in a dry interior and 95 percent in wet or exterior work, verified by lifting a tile and looking, which is why the notch selection here changes the bag count by a factor of four across its range rather than being a detail. Above the 15 in edge that ANSI A108.02 calls large format, three things tighten at once: the substrate flatness tolerance halves to 1/8 in in 10 ft, the mortar has to be a large-and-heavy-tile mix that resists slumping, and back-buttering stops being optional. The joint between the tiles is a separate order with its own arithmetic and is worked out on the grout calculator, and the wall the tile stops against usually wants the drywall and paint figured in the same trip.
What happens to the room you typed in
Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type — measurements, quantities, the prices your supplier quoted you — is uploaded, logged or kept, which is also why the calculators carry on working on a site with no signal.
The tile size, the layout and the box count go nowhere either. No manufacturer finds out that someone in your zip code is pricing 24 in porcelain this week.