The size of grout lines for tile is something that comes up on almost every tile installation. The secret no professional will tell you is there is really no set or absolute proper size for your grout lines. There are some guidelines that need to be followed but the actual size is more of a personal choice than it is a set width.

Grout line guidelines

Since grout line widths are generally a personal preference I’ll let you know what mine are. I separate most tiles into three different categories:

  • Small format tile – Tiles up to and including 8 X 8 inches square.
  • Regular – 12 X 12 up to 16 X 16 inches square.
  • Large format tile – 18 X 18 inches and larger.

These are not technically official category names for tile sizes – it’s just what I call them. I’m weird like that.

Small format tile

A lot of smaller format tiles are self-spacing. That means that on either two or four sides of each tile there are what are called “lugs”. Lugged tile have small bumps or protrusions on the sides which are set directly against the tile next to it. Most of these tiles are made specifically for vertical applications, those are shower walls, backsplashes, etc., rather than floors.

The lugs on the tiles allow them to be stacked atop one another and keep the grout lines consistent throughout the installation. For tiles with lugs on only two sides of each tile you must make sure they are all stacked in the same direction, that the lugs are not butted against each other. Normally the lugs will create grout lines that are 1/32 to 1/16 of an inch.

For small format tiles that do not have lugs I will usually use 1/16″ spacers. Depending upon the texture and consistency of the tiles I may use 1/8″ spacers on occasion. For instance 8 inch slate tiles will usually look better with a slightly larger grout line.

If you prefer larger grout lines but have lugged tiles – don’t panic. You can still use spacers with the lugs. To ensure consistency you need to make sure that you either put the spacers between all the lugs or between the spaces the lugs are not. In other words do not put a spacer between the lugs on one tile and between spaces where there are not lugs on another. To figure out the size of your grout lines you also need to add the size of the lugs to the size of the spacer if you use the spacers between them.

Regular format

Regular format tiles are what I install on most of my jobs. More often than not I will use 1/16″ grout lines on vertical surfaces and 1/8″ lines on floors. I just think it looks better and as long as the tile is consistent enough, that’s what I’ll use. I will usually use the smallest grout line the tile will allow.

The best way to figure out how small you can go is to lay out nine tiles in a square and measure from corner to corner in both directions. If they are within 1/16 inch you can go that small with your grout lines. Some tiles such as slate and some quarry tiles will not be consistent enough to use a grout line that small. The largest grout line I will use is 3/16″ unless otherwise specified by the builder or customer.

Large format

Large format tiles are a bit tricky. These, more than either of the other two, are more dependent upon the tile itself. While most people will purchase larger format tiles specifically because they do not want a lot of grout lines, sometimes the tile will not allow it. Although this is rarely a problem, you need to be aware of it and make sure you check the tiles before you try to go with a very small grout line.

The easiest way to check larger format tiles is simply to measure corner to corner in each direction to ensure squareness. As long as they are the same in both directions, they’re square. Then measure several different tiles from different boxes. With a very good tile you should get exactly the same measurement every time. If that’s the case, you can use a 1/16″ grout line and not have any problems.

Large format tiles with 1/16″ or 1/32″ grout lines and a grout that matches the tile color closely looks great! If done correctly it will almost look like a single large slab of tile.

Which do you prefer?

As you can see there is really no absolute answer. If you like smaller grout lines, as long as the tile will allow it, use them. If you prefer larger, use larger. As a general rule do not go larger than 3/16″ although under certain circumstances such as some slates and quarry tiles, 1/4″ is acceptable.

If you choose to use smaller grout lines you must ensure the tile will allow it. If you don’t you may end up with lines that “jog”. That means the lines will not be perfectly straight and will jump over just a bit with every tile due to inconsistencies in tile sizes.

If you prefer larger grout lines you need to take into consideration the “grid effect”. If you do not use a grout that somewhat matches the tile color you may end up with an installation that looks more like a grid made of grout than tile with a grout accent. The smaller the tile, the more pronounced this effect may become.

No matter which you choose, you must make sure you use the correct type of grout. If your grout is chosen and installed correctly your good tile installation can turn into a great one. Make sure you consider your grout as much as you consider your tile. It can make or break your whole look.

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  • Van

    I inherited 18×18 porcelain tile from a family member which I will be installing on the floor of my kitchen and 2 baths. What size spacing and what type of grout would you use for this tile?
    Many thanks

    • Roger

      Hi Van,

      If you read the article above it will tell you about the spacing. I would likely use 1/8″ provided the tile allows for it. Here is info about the grout: What type of grout to use?

  • James

    I have 13×13 tiles I am laying on a bathroom floor. It is a cheaper tile and the edges are slightly beveled. This means when I put an 1/8″ spacer in, the gap at surface level ends up being just over 3/16″. I prefer the look of 1/8″ grout lines so is there any problem with using 1/16″ spacers to get just over 1/8″ gap at the surface? The tiles sizes are pretty uniform (less than 1/16″ difference measuring 3 diagonally by your method) Would you recommend sanded or unsanded grout?
    Surprisingly I can find no info online about this. I can’t be the first person to notice that beveled edges make the spacing/grout rules ambiguous. Thank You!

    • Roger

      Hi James,

      With beveled edges the grout is intended to be flush with the bottom corner of the bevel, not with the surface of the tile. So your grout lines will still be whatever size spacer you use. If you try to grout flush with the surface of the tile the grout over the edge of that bevel will eventually crack out, since it doesn’t really have anything to bond to long-term. Then you end up with grout lines with cracks all the way along the edge. Yes, you can use 1/16″ spacers if you want, but the grout will still need to be only flush with the bottom edge of the bevel.

      • James

        Thanks for the reply but I may not have been entirely clear. This is just completely standard run of the mill square floor tile. “Beveled” may have been the wrong word since I am not talking about an intentional design feature, just the fact that the raw edges flare out slightly as a side effect of manufacturing. If you looked at the tile in profile is very slightly trapezoidal, not rectangular. Therefore if I push a 1/16″ spacer all the way to the floor, the gap at surface level is closer to 1/8″.

        • Roger

          Ah, gotcha. You will need to have space between them, but you can use as small a spacer as you want. You just want to ensure that the tiles are not butted to one another.

  • victoria

    I attemoted my first tile job in guest bathrroom floor. It is small just 5X5. We used 12X24 high gloss porcelein tiles with 1/16 grout lines. I just finished the grout work but now i am nervous I did not “smoosh” enough polyblend into the grout line. I used grout float at 45 degree angle to fill but now I am wondering if I had enough “passes” over the lines. What are your thoughts on this? Obviously, I can not see the lines to see if they are 2/3 of tile full. I am guessing the worst that would happen is grout would eventually crack and I would have to scrape out old and replace with new. I am really not interested in that due to rectified edges but I guess time will tell Thanks.

    • Roger

      Hi Victoria,

      If you have any areas that have a ‘bridge’ of grout, it will normally show within the first week. If you have any lines that are not full enough, it will show the next day after the grout cures. It will be a shallow spot in the grout itself, and it will be noticeable. If you don’t see that you’re fine.

  • Johnny

    I’m using a 4×8 glaze wall tile with lugs/tabs what’s the joint size recommendation for that particular tile please advise

    • Roger

      Hi Johnny,

      The correct way to install those is to stack them on one another. The lugs create the grout line – normally a bit over 1/32.

      • Johnny

        Yea a 1/16 of an inch at the showers

  • Pam

    I am installing a Marazzi 6×36 mixed with 9×36 wood look tile ( cathedral heights nobility ) in entry kitchen family , laundry and bath. I was told by installer he recommends 1/8 over 1/16 said don’t get the possible wavy joints .. I like the more wood look but want to do what’s best. Also said use a maupi colorfast grout. Keeps color better without constant sealing. Thoughts

    • Roger

      Hi Pam,

      Your installer is correct on both counts. With tile that size you need a larger grout line due to inconsistencies in the cooling process of the tile. Larger grout lines will compensate for that. Mapei does not have a grout called ‘colorfast’ (not sure what particular grout you’re referring to), but they do have a few different color-consistent grouts that work very well.