The gap between tiles, the grout joint, is set by the tile, not by taste alone. Tiles are never perfectly uniform in size, and the joint has to be wide enough to absorb that variation so the lines stay straight. This guide explains the rule the tile industry uses, gives typical joint widths for common tiles, and shows how the choice changes the amount of grout you need. For tile, box and thinset counts, use the tile calculator.
The rule: three times the size variation, never under 1/16 in
The American National Standard for installing ceramic tile (ANSI A108.02, as summarised by the Tile Council of North America) sets the minimum grout joint at three times the actual variation in facial dimensions of the tiles being used, and never less than 1/16 in. In plain terms: if the tiles in your boxes differ in length or width by up to 1/32 in, the joint should be at least 3/32 in, so round up to 1/8 in. Pressed ceramic tile with cushioned edges varies more than rectified porcelain, which is ground to size after firing and can go down to the 1/16 in minimum.
To check your tiles, take a dozen from different boxes, line them up against a straightedge, and measure the longest and shortest. The difference is the variation. Do it before you buy spacers, because the tile manufacturer’s recommended joint (often printed on the box) is based on the same idea.
Typical joint widths
| Tile | Typical joint | Why |
|---|---|---|
| Rectified porcelain (12 x 24, 24 x 24 and larger) | 1/16 to 1/8 in | Ground edges vary little; wider joints are a design choice. |
| Pressed ceramic or non-rectified porcelain floor tile | 1/8 to 3/16 in | Allows for the larger size variation of unground edges. |
| Subway tile (3 x 6 in) and small wall tile | 1/16 to 1/8 in | Many have built-in lugs that set the joint. |
| Handmade, terracotta, saltillo, natural cleft stone | 3/16 to 1/2 in | Large variation in size and shape. |
| Mosaic sheets | As set by the sheet | The mesh fixes the joint; match it between sheets. |
Large tiles and offsets
Large-format tiles (any edge 15 in or longer) are rarely perfectly flat; most have a slight bow along their length. Laid in a running bond with the joints offset by half a tile, the high centre of one tile sits next to the low end of its neighbour, and the edges do not line up (lippage). The industry guidance in A108.02 therefore limits the offset for tiles with an edge longer than 18 in to no more than 33% of the tile length unless the manufacturer says otherwise, which is why 12 x 24 tiles are usually laid at a one-third offset. Leveling clips help, but they do not fix a bowed tile.
Grout needed per 100 sq ft
| Tile | 1/16 in joint | 1/8 in joint | 3/16 in joint | 1/4 in joint |
|---|---|---|---|---|
| 3 x 6 in subway (1/4 thick) | 6.5 lb | 13.0 lb | 19.5 lb | 26.0 lb |
| 4 x 4 in (1/4 thick) | 6.5 lb | 13.0 lb | 19.5 lb | 26.0 lb |
| 12 x 12 in (3/8 thick) | 3.3 lb | 6.5 lb | 9.8 lb | 13.0 lb |
| 12 x 24 in (3/8 thick) | 2.4 lb | 4.9 lb | 7.3 lb | 9.8 lb |
| 24 x 24 in (3/8 thick) | 1.6 lb | 3.3 lb | 4.9 lb | 6.5 lb |
Small tiles and wide joints use far more grout: 3 x 6 in subway tile with 1/8 in joints takes about 8 times as much grout per square foot as 24 x 24 in tile with 1/16 in joints. Sanded grout is generally used for joints of 1/8 in and wider and unsanded grout for narrower joints; epoxy and other high-performance grouts have their own joint ranges on the label.
Practical tips
- Movement joints: leave a gap at walls, at changes of plane (inside corners of showers) and across large floors, filled with flexible sealant rather than grout. The TCNA guide and the tile maker set the spacing.
- Spacers: buy spacers to the joint you chose, but treat them as a guide; set to a layout line every few rows so small errors do not add up.
- Walls: for subway tile, a 1/16 in joint looks crisp, but only if the tiles are very consistent; check a box first.
- Grout colour: a grout close to the tile colour makes small variations in joint width less visible.
Frequently asked questions
What is the standard spacing for floor tiles?
About 1/8 to 3/16 in for most pressed ceramic or non-rectified porcelain, and 1/16 to 1/8 in for rectified porcelain. The minimum is three times the size variation of the tiles and never less than 1/16 in (ANSI A108.02).
What size spacer for 12×24 tile?
For rectified 12 x 24 in porcelain, 1/16 to 1/8 in is typical; for non-rectified, 1/8 to 3/16 in. Lay it at no more than a one-third offset to limit lippage.
What spacing for subway tile?
1/16 to 1/8 in for 3 x 6 in subway tile, or the joint set by the tile’s built-in lugs.
Can tile be laid with no grout lines?
No. Even rectified tile needs at least a 1/16 in joint to absorb size variation and movement; tight-butted tile tends to chip and tent.
Sources
- ANSI A108.02, General Requirements: Materials, Environmental, and Workmanship (installation of ceramic tile), grout joint size and offset provisions, as summarised by the Tile Council of North America (TCNA Handbook); paraphrased, not reproduced.
- Grout volume formula: the joint-volume method used by grout makers and by our tile calculator (grout at about 1.6 kg/L).
Last reviewed: 24 October 2026. Numbers in the tables are our arithmetic from the sources listed; code sections are summarised, not quoted. How we check our work: methodology and corrections. Spotted an error? Please let us know.