Should I lay tile from the wall or from the centre of the room?

Centred, for almost any room anyone will look at as a whole. It puts an even cut tile at both edges instead of a full tile at one wall and a leftover sliver at the other, and a floor with two matching narrow borders reads as designed while a floor with one thin strip at one side reads as a mistake nobody caught in time.

How wide should a grout joint be?

1/16" for rectified (precision-cut) tile with sharp, consistent edges, and 3/16" to 1/4" for standard tile whose edges vary enough that a tight joint would telegraph every difference. Bigger tile generally wants a slightly wider joint too, so more of an inevitable edge variation is absorbed by the grout line rather than showing as a wavy line between tiles.

How much extra tile should I buy?

Ten percent for a straightforward grid layout, and more for anything that adds cuts: fifteen for a diagonal layout, more again for herringbone or a room with a lot of jogs, niches or doorways. Buy it all from one production run — tile is dye-lotted the way flooring is, and a box ordered later to make up a shortfall will not match.

How wide can a cut tile at the edge be before it looks wrong?

Under about 2" reads as an afterthought and is hard to set and grout cleanly besides — a sliver that thin chips easily and barely holds its own grout joint. If a layout leaves one, shifting the starting line by an inch or two, or switching between a centred and an edge-start layout, usually finds a wider cut.

Why does the tile count assume a rectangular grid?

Because that is the layout a full box of square or rectangular tile is sold for, and it is the one every other figure on this page — grout joint, waste factor, cut width — assumes too. A herringbone, basketweave or diagonal pattern cuts differently and wastes more, and needs its own waste allowance layered on top of what this calculator gives you.

Tile calculator

Enter the room and the tile size, and see how the grid actually falls: full tiles across the middle, a sized cut tile at each edge, and the box count to buy. Check your spacers against the true-size grout gauge below before setting the first tile.

Room width

Room length

Tile width

Tile length

Layout

Advanced settings3/16" grout · 10% waste · 9 a box

Grout joint

= 0.188"

Waste

Tiles per box

120 sq ft

158tiles

Boxes

Cut tile, one side

5 1/16"

Cut tile, other side

4 7/8"

Order this

Tiles, with waste143 to fill the floor, 10% added for cuts: 158
Boxes9 tiles a box: 18
Across the roomCut tile 5 1/16" wide: 9 full + cut
Down the roomCut tile 4 7/8" wide: 11 full + cut

Before you cut

No cut tile under 2" — passesEvery cut tile is wide enough to set and grout cleanly.

Grout joint, at true size

Print at 100%, check the ruler, then compare it to your tile spacers before setting the first tile — a spacer bag marked in a round metric size is not always the fraction it claims to be.

Check this first

Put a tape on the printed ruler. If it does not read exactly 6 inches, the print was scaled — set the print dialog to 100% or “Actual size” and print it again. Do not cut wood from a template that failed this.

Grout joint width

Hold a spacer against this before you set the first tile — the layout above assumes every joint is exactly this wide.

Why centred

Starting from the centre of the room puts a matching cut tile at both walls instead of a full tile at one and a sliver at the other, which is the layout that reads as planned rather than improvised in a room anyone sees as a whole.

Where to buy this

18 boxes — 158 tilesHome Depot Lowe's

Buy the whole room at once and check the lot number on the boxes: two lots of the same tile are close, and a floor shows the difference.

Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.

Worked example: 12" × 12" tile

A floor 120" × 144" in 12" × 12" tile with 3/16" grout joints, laid centred on the room, has 9 full tiles one way and 11 the other.

The cut tiles are 5 1/16" at both walls one way and 4 7/8" at both walls the other.

That is 143 tiles, 158 with 10% waste — 18 boxes of 9.

Tiles: 143
With 10% waste: 158
Boxes: 18
Cut tile, one way: 5 1/16"
Cut tile, the other: 4 7/8"

These are the figures the calculator above opens on. Change any field and it works the same problem for your numbers.

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About laying tile

Should I lay tile from the wall or from the centre of the room?: Centred, for almost any room anyone will look at as a whole. It puts an even cut tile at both edges instead of a full tile at one wall and a leftover sliver at the other, and a floor with two matching narrow borders reads as designed while a floor with one thin strip at one side reads as a mistake nobody caught in time.
How wide should a grout joint be?: 1/16" for rectified (precision-cut) tile with sharp, consistent edges, and 3/16" to 1/4" for standard tile whose edges vary enough that a tight joint would telegraph every difference. Bigger tile generally wants a slightly wider joint too, so more of an inevitable edge variation is absorbed by the grout line rather than showing as a wavy line between tiles.
How much extra tile should I buy?: Ten percent for a straightforward grid layout, and more for anything that adds cuts: fifteen for a diagonal layout, more again for herringbone or a room with a lot of jogs, niches or doorways. Buy it all from one production run — tile is dye-lotted the way flooring is, and a box ordered later to make up a shortfall will not match.
How wide can a cut tile at the edge be before it looks wrong?: Under about 2" reads as an afterthought and is hard to set and grout cleanly besides — a sliver that thin chips easily and barely holds its own grout joint. If a layout leaves one, shifting the starting line by an inch or two, or switching between a centred and an edge-start layout, usually finds a wider cut.
Why does the tile count assume a rectangular grid?: Because that is the layout a full box of square or rectangular tile is sold for, and it is the one every other figure on this page — grout joint, waste factor, cut width — assumes too. A herringbone, basketweave or diagonal pattern cuts differently and wastes more, and needs its own waste allowance layered on top of what this calculator gives you.

You might also need

Read up, or take it to the shop

Tile quantity chart — printable chart