Tile Grout Chart: Joint Width by Tile Size (mm & in)

What does a 12×24 in tile taking a 1/4 in joint mean?

On the default — a 12×24 in tile — the grout joint is 1/4 in (6.35 mm). The tile’s longest side is 24 in, which falls in the over-12-in-to-24-in band, and that band takes a 1/4 in joint. Whether that is the right joint depends on the tile — a rectified tile can take the narrow end of its band, and a warped tile needs a wider joint — but the chart is the starting point the trade works from.

Three things about the model are worth stating plainly.

First, the joint is 1/4 in and the tile is 12×24 in — the joint and the tile are two outputs, never the same number. Second, the meaning is 1/4 in of grout between 12×24 in tiles — the gap that hides lippage and lets the tiles move a little with temperature, not the tile itself. And third, the joint is a step function of the longest side: a 12 in tile takes a 3/16 in joint, but a 12.1 in tile takes a 1/4 in joint — one tenth of an inch crosses the step — all listed in Accuracy & limitations.

The full chart

Mosaic 1×1 in: longest side 1 in — grout joint 1/16 in (1.59 mm).

2×2 in: longest side 2 in — grout joint 1/16 in (1.59 mm).

4×4 in: longest side 4 in — grout joint 1/8 in (3.18 mm).

6×6 in: longest side 6 in — grout joint 1/8 in (3.18 mm).

8×8 in: longest side 8 in — grout joint 1/8 in (3.18 mm).

12×12 in: longest side 12 in — grout joint 3/16 in (4.76 mm).

12×24 in: longest side 24 in — grout joint 1/4 in (6.35 mm).

18×18 in: longest side 18 in — grout joint 1/4 in (6.35 mm).

24×24 in: longest side 24 in — grout joint 1/4 in (6.35 mm).

24×48 in: longest side 48 in — grout joint 3/8 in (9.53 mm).

Adjustment notes — rectified tile, lippage, grout type

Rectified tile. Rectified tile is cut square after firing, so its edges are true and it can take the narrow end of its band — a rectified 12×24 in tile can take a 1/8 in joint where an unrectified one needs 1/4 in. Check the tile maker’s own minimum before you narrow the joint.

Lippage. Large-format tile is rarely perfectly flat, so a wider joint lets the installer even out the small height differences between tiles. A 24×48 in tile with a warped face needs the full 3/8 in joint, and a flat one can take less.

Grout type. Sanded grout suits joints 1/8 in and wider; unsanded grout suits joints under 1/8 in. A 1/16 in mosaic joint needs unsanded grout, and a 1/4 in large-format joint needs sanded grout.

Movement. Tiles expand and contract with temperature, so the joint is also a movement joint — a floor over underfloor heating needs the wide end of its band, not the narrow end.

The worked example, line by line

Setup: tile size 12×24 in.

Line 1 — the longest side. The longest side of a 12×24 in tile is 24 in.

Line 2 — the band. 24 in falls in the over-12-in-to-24-in band.

Line 3 — the joint. That band takes a 1/4 in grout joint.

Line 4 — the millimetres. 1/4 in × 25.4 = 6.35 mm.

Line 5 — the check. At 12 in the joint is 3/16 in — and at 12.1 in it is 1/4 in.

Every branch, checked

Mosaic 1×1 in tile: Mosaic 1×1 in tile: 1/16 in (1.59 mm) grout joint

2×2 in tile: 2×2 in tile: 1/16 in (1.59 mm) grout joint

4×4 in tile: 4×4 in tile: 1/8 in (3.18 mm) grout joint

6×6 in tile: 6×6 in tile: 1/8 in (3.18 mm) grout joint

8×8 in tile: 8×8 in tile: 1/8 in (3.18 mm) grout joint

12×12 in tile: 12×12 in tile: 3/16 in (4.76 mm) grout joint

12×24 in tile: 12×24 in tile: 1/4 in (6.35 mm) grout joint

24×48 in tile: 24×48 in tile: 3/8 in (9.53 mm) grout joint

The reverses, worked backwards

Smallest longest side where the joint reaches 1/8 in: At the displayed 2.1 in the figures are Tile with a 2.10 in longest side: 1/8 in (3.18 mm) grout joint — longest side 2.10 in. At 2.0 in the figures are 2×2 in tile: 1/16 in (1.59 mm) grout joint — longest side 2 in — the joint is 1/16 in — so 2.1 in is the smallest longest side where the joint reaches 1/8 in.

Smallest longest side where the joint reaches 3/16 in: At the displayed 8.1 in the figures are Tile with a 8.10 in longest side: 3/16 in (4.76 mm) grout joint — longest side 8.10 in. At 8.0 in the figures are 8×8 in tile: 1/8 in (3.18 mm) grout joint — longest side 8 in — the joint is 1/8 in — so 8.1 in is the smallest longest side where the joint reaches 3/16 in.

Smallest longest side where the joint reaches 1/4 in: At the displayed 12.1 in the figures are Tile with a 12.10 in longest side: 1/4 in (6.35 mm) grout joint — longest side 12.10 in. At 12.0 in the figures are 12×12 in tile: 3/16 in (4.76 mm) grout joint — longest side 12 in — the joint is 3/16 in — so 12.1 in is the smallest longest side where the joint reaches 1/4 in.

Smallest longest side where the joint reaches 3/8 in: At the displayed 24.1 in the figures are Tile with a 24.10 in longest side: 3/8 in (9.53 mm) grout joint — longest side 24.10 in. At 24.0 in the figures are 12×24 in tile: 1/4 in (6.35 mm) grout joint — longest side 24 in — the joint is 1/4 in — so 24.1 in is the smallest longest side where the joint reaches 3/8 in.

Largest longest side that still takes a 1/16 in joint: At the displayed 2.0 in the figures are 2×2 in tile: 1/16 in (1.59 mm) grout joint — longest side 2 in. At 2.1 in the figures are Tile with a 2.10 in longest side: 1/8 in (3.18 mm) grout joint — longest side 2.10 in — the joint is 1/8 in — so 2.0 in is the largest longest side that still takes a 1/16 in joint.

Largest longest side that still takes a 1/4 in joint: At the displayed 24.0 in the figures are 12×24 in tile: 1/4 in (6.35 mm) grout joint — longest side 24 in. At 24.1 in the figures are Tile with a 24.10 in longest side: 3/8 in (9.53 mm) grout joint — longest side 24.10 in — the joint is 3/8 in — so 24.0 in is the largest longest side that still takes a 1/4 in joint.

A warning about the neighbours: every neighbour above sits a tenth of an inch from the star, and every neighbour figure is a different joint even though the tile barely changed — the step, not the exact size, decides. The page prints the full chart so the rounding does not mislead you: R1 2.1 / 2.0 in; R2 8.1 / 8.0 in; R3 12.1 / 12.0 in; R4 24.1 / 24.0 in; R5 2.0 / 2.1 in; R6 24.0 / 24.1 in.

What the defaults assume

The defaults are a 12×24 in tile — 12×24 in tile: 1/4 in (6.35 mm) grout joint. With Mosaic 1×1 in tile, Mosaic 1×1 in tile: 1/16 in (1.59 mm) grout joint. With 2×2 in tile, 2×2 in tile: 1/16 in (1.59 mm) grout joint. With 4×4 in tile, 4×4 in tile: 1/8 in (3.18 mm) grout joint. With 6×6 in tile, 6×6 in tile: 1/8 in (3.18 mm) grout joint. With 8×8 in tile, 8×8 in tile: 1/8 in (3.18 mm) grout joint. With 12×12 in tile, 12×12 in tile: 3/16 in (4.76 mm) grout joint. With 12×24 in tile, 12×24 in tile: 1/4 in (6.35 mm) grout joint. With 24×48 in tile, 24×48 in tile: 3/8 in (9.53 mm) grout joint. With 0 in, Enter your tile size in inches. — no tile to grout — the calculator says so plainly. With 0.5 in, Tile with a 0.50 in longest side: 1/16 in (1.59 mm) grout joint — longest side 0.50 in — the smallest tile there is — 1/16 in. With 2.0 in, 2×2 in tile: 1/16 in (1.59 mm) grout joint — longest side 2 in — the top of the first band — still 1/16 in. With 2.01 in, Tile with a 2.01 in longest side: 1/8 in (3.18 mm) grout joint — longest side 2.01 in — one hundredth of an inch over the step — 1/8 in. With 8.0 in, 8×8 in tile: 1/8 in (3.18 mm) grout joint — longest side 8 in — the top of the second band — still 1/8 in. With 8.01 in, Tile with a 8.01 in longest side: 3/16 in (4.76 mm) grout joint — longest side 8.01 in — one hundredth of an inch over the step — 3/16 in. With 12.0 in, 12×12 in tile: 3/16 in (4.76 mm) grout joint — longest side 12 in — the top of the third band — still 3/16 in. With 12.01 in, Tile with a 12.01 in longest side: 1/4 in (6.35 mm) grout joint — longest side 12.01 in — one hundredth of an inch over the step — 1/4 in. With 24.0 in, 12×24 in tile: 1/4 in (6.35 mm) grout joint — longest side 24 in — the top of the fourth band — still 1/4 in. With 24.01 in, Tile with a 24.01 in longest side: 3/8 in (9.53 mm) grout joint — longest side 24.01 in — one hundredth of an inch over the step — 3/8 in. With 36 in, Tile with a 36 in longest side: 3/8 in (9.53 mm) grout joint — longest side 36 in — above the table — 3/8 in. With 60 in, Tile with a 60 in longest side: 3/8 in (9.53 mm) grout joint — longest side 60 in — far above the table — 3/8 in.

A note on the rounding: the millimetres are the inch fractions times 25.4, to two decimals — 1/16 in is 1.59 mm, 1/8 in is 3.18 mm, 3/16 in is 4.76 mm, 1/4 in is 6.35 mm and 3/8 in is 9.53 mm. With a fractional tile size the joint still lands on one of the five bands — 2.01 in takes a 1/8 in joint — and the page prints the band so the rounding does not mislead you.

Output · formula · meaning

Who uses this

• The homeowner tiling a bathroom: they learn a 12×24 in tile takes a 1/4 in (6.35 mm) joint — and they check the 12 in branch to see how close they are to the next joint down.
• The DIYer buying grout: they learn the joint width for their tile — and they check whether they need sanded or unsanded grout.
• The tile setter: they learn the joint for every tile size in the job — and they check the reverses to see where each joint steps up.
• The kitchen remodeler: they learn a mosaic backsplash takes a 1/16 in joint — and they check the adjustment notes to see whether their tile is rectified.

Accuracy & limitations

The calculator does the arithmetic exactly — longest side into the band, band into the joint, joint into millimetres — and every figure on this page is checked against an independent model. The bands follow the standard guidance in the trade, so the chart and the lookup agree. What it cannot do is override the tile maker: the manufacturer’s own instructions come first, and a tile with a warped face needs a wider joint than the chart says. A rectified tile can take a narrower joint than the chart says, and a floor over underfloor heating needs the wide end of its band. For a final purchase, check the tile maker’s specification.

Cite this calculator

Grout joint by tile size (longest side): up to 2 in — 1/16 in (1.59 mm); over 2 in to 8 in — 1/8 in (3.18 mm); over 8 in to 12 in — 3/16 in (4.76 mm); over 12 in to 24 in — 1/4 in (6.35 mm); over 24 in — 3/8 in (9.53 mm). On the defaults — a 12×24 in tile — the grout joint is 1/4 in (6.35 mm). Smallest longest side where the joint reaches 1/8 in: 2.1 in. Smallest longest side where the joint reaches 3/16 in: 8.1 in. Smallest longest side where the joint reaches 1/4 in: 12.1 in. Smallest longest side where the joint reaches 3/8 in: 24.1 in. Largest longest side that still takes a 1/16 in joint: 2.0 in. Largest longest side that still takes a 1/4 in joint: 24.0 in. Source: Bright Side Kit, brightoolbox.com.

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