The right trowel size for tile depends on the tile size, tile back, substrate and the mortar coverage you achieve. As a starting point, small mosaics typically require a small V notch or square notch, 3 x 6 subway tile commonly uses a 1/4 x 1/4 inch square notch, 12 x 12 tile often starts with a 1/4 x 3/8 inch square notch, and 12 x 24 porcelain tile commonly requires a deeper notch such as a 1/4 x 1/2 inch U notch.
Those sizes are starting points, not absolute rules. The correct trowel is the one that produces adequate mortar contact underneath your specific tile without excessive mortar squeezing into the grout joints.
At BELK Tile, my advice is simple: use the chart below to choose your starting trowel, set a test tile, pull it back up and check the mortar coverage. That final inspection tells you whether your trowel size and installation technique are working.
Tile Trowel Size Chart
Use this tile trowel size chart as a starting point. Always follow the installation requirements of your tile and setting material manufacturers and verify actual mortar coverage during installation.
| Tile Size or Type | Recommended Starting Trowel | Typical Application |
|---|---|---|
| Thin glass mosaic | 1/8 x 1/8 inch square notch or manufacturer recommendation | Backsplashes and walls |
| Penny round and small hex mosaic | 3/16 inch square notch or small V notch | Shower floors, backsplashes and walls |
| 2 x 2 mosaic tile | 1/4 x 1/4 inch square notch | Shower floors, floors and walls |
| 3 x 6 subway tile | 1/4 x 1/4 inch square notch | Backsplashes and walls |
| 4 x 12 or 4 x 16 subway tile | 1/4 x 3/8 inch square notch | Backsplashes and walls |
| 6 x 6 ceramic tile | 1/4 x 1/4 inch square notch | Walls and floors |
| 12 x 12 tile | 1/4 x 3/8 inch square notch | Walls and floors |
| 12 x 24 porcelain tile | 1/4 x 1/2 inch U notch or manufacturer recommended large format trowel | Floors and walls |
| Porcelain plank tile | 1/4 x 1/2 inch U notch or specialty large format notch | Floors and walls |
| Large format tile | 1/2 inch deep, U notch, Euro notch or manufacturer specified trowel | Floors and walls |
Mike's Tip: Never assume a trowel is correct just because your tile size appears on a chart. Pull up one of your first tiles and inspect the back. If you are not achieving adequate mortar contact, adjust your trowel size or installation technique before continuing.
What Size Trowel Should I Use for Tile?
The correct tile trowel is the smallest appropriate notch that consistently produces the required mortar coverage underneath the tile.
Tile dimensions provide a useful starting point, but they do not tell the entire story. You should also consider:
- Tile thickness
- Size of the tile
- Shape and depth of the tile back
- Tile warpage
- Flatness of the substrate
- Type of mortar being used
- Whether the installation is dry, wet or exterior
Two 12 x 24 porcelain tiles can require different approaches. One may have a relatively flat back while another has deep ribs or slight crowning through the center. The same tile can also behave differently when installed over two different substrates.
The tile size tells you where to start. The mortar coverage tells you whether you are right.
How Much Mortar Coverage Should Tile Have?
Mortar coverage is one of the most important factors in determining whether you selected the correct trowel.
As a general benchmark:
- Interior dry installations: More than 80 percent mortar contact.
- Showers and other wet areas: More than 95 percent mortar contact.
- Exterior tile installations: More than 95 percent mortar contact.
- Natural stone: Greater than 95 percent mortar contact.
You also want good mortar contact around the tile edges and corners without significant continuous voids underneath the tile.
This is why mortar coverage matters more than simply memorizing trowel sizes.
How Does a Notched Tile Trowel Work?
A notched trowel controls how much mortar is placed between the tile and substrate.
First, use the flat side of the trowel to firmly work mortar into the substrate. This is commonly referred to as keying the mortar into the surface.
Additional mortar is then applied and combed using the notched side of the trowel. The notches create consistent mortar ridges.
When the tile is pressed into the fresh mortar and moved across those ridges, the ridges collapse and spread across the back of the tile.
A deeper notch generally deposits more mortar. That does not mean a larger notch is always better. Too much mortar can cause excessive squeeze through, uneven tile height and unnecessary cleanup.
The goal is to use enough mortar to achieve proper coverage without applying more than the installation requires.
What Do Tile Trowel Measurements Mean?
Tile trowels are identified by the dimensions and shape of their notches.
For example, a 1/4 x 1/4 inch square notch trowel has square notches approximately 1/4 inch wide and 1/4 inch deep.
A 1/4 x 3/8 inch trowel has deeper notches and generally deposits more mortar.
The most common tile trowel styles include square notch, V notch, U notch and specialty notch trowels.
Square Notch Trowel
Square notch trowels are among the most commonly used trowels for ceramic and porcelain tile.
Common sizes include 1/4 x 1/4 inch and 1/4 x 3/8 inch. These work well with many subway tiles and small to medium format tiles.
V Notch Trowel
V notch trowels generally deposit less mortar and are useful with thin mosaics and applications where excessive mortar could push into the grout joints.
U Notch Trowel
A U notch creates rounded mortar ridges. Deeper U notch trowels, including 1/4 x 1/2 inch options, are commonly used with larger tile.
Euro and Specialty Notch Trowels
Euro notch, slant notch and other specialty trowels are designed to help mortar ridges collapse efficiently.
They are commonly used with large format porcelain and other installations where achieving consistent mortar contact is particularly important.
What Size Trowel for 12 x 24 Tile?
For most 12 x 24 porcelain tile installations, a 1/4 x 1/2 inch U notch is a strong starting point. A Euro notch or another large format trowel recommended by the mortar manufacturer may also be appropriate.
Large tile requires extra attention because it can bridge small variations in the floor or wall. Porcelain tile may also have slight warpage or crowning that makes it more difficult for mortar to contact the entire back.
For this reason, I recommend back buttering most 12 x 24 tiles.
Use the flat side of your trowel to firmly apply a thin coat of mortar across the back of the tile before setting it into the combed mortar.
The purpose is not to create another thick mortar layer. You are filling the texture and irregularities on the back of the tile to improve contact.
Learn more in our guide to back buttering tile.
What Size Trowel for 12 x 12 Tile?
A 1/4 x 3/8 inch square notch is a good starting point for many 12 x 12 ceramic and porcelain tiles.
A very flat tile installed over a properly prepared substrate may require less mortar, while natural stone or tile with a pronounced back pattern may require more.
Pull up one of your first tiles and inspect the mortar transfer before continuing.
What Size Trowel for Subway Tile?
A 1/4 x 1/4 inch square notch is a practical starting point for traditional 3 x 6 subway tile.
As subway tile becomes larger, such as 4 x 12 or 4 x 16, a 1/4 x 3/8 inch square notch is often a better starting point.
Remember that the tile back matters too. A subway tile with deep ribs or lugs may require more mortar than a smooth backed tile of the same dimensions.
What Size Trowel for 3 x 6 Subway Tile?
Start with a 1/4 x 1/4 inch square notch for most 3 x 6 subway tile installations. Set a test tile and check mortar coverage before continuing.
What Size Trowel for 4 x 12 Subway Tile?
A 1/4 x 3/8 inch square notch is a useful starting point for many 4 x 12 ceramic and porcelain subway tiles.
What Size Trowel for Mosaic Tile?
Small mosaic tiles typically require a smaller notch than standard field tile because excessive mortar can squeeze through the numerous grout joints.
For very small mosaics such as penny rounds and small hexagons, a small V notch or square notch is generally the best starting point.
For many 2 x 2 mosaics, a 1/4 x 1/4 inch square notch can work well.
After placing a mesh mounted mosaic sheet into the mortar, gently press the sheet into a consistent plane using a grout float or beating block.
Avoid pressing so hard that mortar fills the grout joints.
For more installation advice, read our mesh mounted mosaic tile installation guide.
What Size Trowel for Penny Tile?
A small V notch or approximately 3/16 inch square notch is a good starting point for many thin penny round mosaics.
The goal is to achieve good contact underneath every individual piece without applying so much mortar that it fills the grout joints.
What Size Trowel for Shower Floor Tile?
Shower floors commonly use smaller mosaics because the individual pieces can follow the slope toward the drain.
Small penny rounds and hexagon mosaics generally require a small V notch or square notch. Larger 2 x 2 shower floor mosaics commonly start with a 1/4 x 1/4 inch square notch.
Because the shower floor is a wet installation, you should aim for greater than 95 percent mortar contact.
See our shower floor tile installation guide for more information about layout, setting and working around the drain.
What Size Trowel for Shower Wall Tile?
There is no single trowel size specifically for shower walls. The tile dimensions and back profile determine your starting notch.
A small ceramic wall tile may use a 1/4 x 1/4 inch square notch, while a 12 x 24 porcelain shower tile generally requires a deeper notch.
The important difference is coverage. Because a shower is a wet area, aim for greater than 95 percent mortar contact.
For larger porcelain tile, back buttering and periodic coverage checks are particularly important.
Read our guide to installing porcelain tile on shower walls for additional installation information.
What Size Trowel for Large Format Tile?
Large format tile commonly requires a 1/4 x 1/2 inch U notch, Euro notch or another large format trowel recommended by the mortar manufacturer.
The larger the tile becomes, the more important substrate preparation becomes.
Large tile cannot easily follow variations in the floor or wall. A bigger trowel should not be used as a substitute for properly flattening an uneven substrate.
Correct significant low spots, humps and other irregularities before beginning the tile installation.
What Size Trowel for Porcelain Plank Tile?
Long porcelain plank tiles, including common wood look formats, generally require a deeper notch than small format tile.
A 1/4 x 1/2 inch U notch or specialty large format trowel is a good starting point for many installations.
Porcelain planks can have slight crowning through their length, which makes substrate preparation, mortar coverage and back buttering especially important.
What Size Trowel for Glass Tile?
Glass tile requires extra attention because translucent or semitranslucent glass can reveal mortar irregularities behind the finished tile.
Thin glass mosaics generally require a small square notch. Larger glass tile may need a larger notch depending on the tile size, thickness and manufacturer instructions.
White mortar is commonly recommended behind translucent and light colored glass because gray mortar can affect the finished appearance.
For some translucent glass installations, mortar ridges should be flattened before the tile is set so that trowel marks and voids are not visible through the face.
Always follow the installation instructions supplied by the glass tile and setting material manufacturers.
Does Tile Material Determine Trowel Size?
Not by itself.
You should not choose a particular trowel simply because the tile is ceramic, porcelain, natural stone or glass.
Material affects the decision because different products have different sizes, thicknesses, weights, back profiles and installation requirements.
Ceramic Tile
Many standard ceramic wall tiles work well with a 1/4 x 1/4 inch square notch as a starting point.
Porcelain Tile
Porcelain tile ranges from small mosaics to oversized panels. Choose the trowel according to the actual tile format and required coverage rather than simply because the tile is porcelain.
Natural Stone Tile
Natural stone may have variations in thickness and texture on the back. High mortar coverage and back buttering are commonly important.
Glass Tile
Glass requires careful mortar selection, troweling and coverage because imperfections behind translucent tile may remain visible after installation.
How to Check Mortar Coverage Under Tile
This is one of the most important steps in choosing the correct trowel, and it only takes a few minutes.
- Use the flat side of your trowel to firmly key mortar into the substrate.
- Apply additional mortar.
- Comb straight, parallel ridges using the notched side of the trowel.
- Set the tile into the fresh mortar before the mortar begins to skin over.
- Move the tile back and forth perpendicular to the mortar ridges.
- Lift the tile back up.
- Inspect the back of the tile for mortar transfer and voids.
If substantial areas of the tile back have little or no mortar contact, something needs to change.
You may need to adjust your trowel angle, use a larger notch, back butter the tile, improve your embedding technique or correct an uneven substrate.
Check your first few tiles and continue checking periodically during the installation.
Which Direction Should You Trowel Thinset?
Comb thinset into straight, parallel ridges rather than swirling the mortar.
After placing the tile, move it perpendicular to the direction of the ridges.
This helps the mortar ridges collapse and gives trapped air a path to escape from underneath the tile.
With rectangular tile, combing the ridges parallel to the shorter side can shorten the distance that trapped air needs to travel.
Should You Back Butter Tile?
Back buttering means applying a thin coat of mortar directly to the back of the tile using the flat side of the trowel.
I particularly recommend checking the need for back buttering with large format porcelain, porcelain plank tile, natural stone and tile with pronounced patterns or depressions on the back.
The purpose is not to pile additional mortar onto the tile. You are filling the texture on the tile back to improve contact with the mortar on the substrate.
Can a Tile Trowel Be Too Small?
Yes. If you lift a test tile and find substantial areas without mortar transfer, your trowel may not be depositing enough mortar.
Before automatically moving to a larger notch, confirm that your troweling and embedding technique is correct.
If coverage remains insufficient, a deeper notch may be appropriate.
Can a Tile Trowel Be Too Big?
Yes. Bigger is not automatically better.
If excessive mortar continually pushes through the grout joints, makes it difficult to maintain consistent tile height or creates unnecessary mortar buildup, you may be using a larger notch than the installation requires.
This is particularly noticeable with mosaic tile.
Common Tile Trowel Mistakes to Avoid
Choosing a Trowel Based Only on Tile Dimensions
Tile size is the starting point, not the entire answer. The tile back, substrate, mortar and installation conditions also matter.
Never Checking Mortar Coverage
A tile can feel firmly set while still having substantial voids underneath it. Lift your first few tiles and check them.
Swirling the Mortar
Swirled mortar can trap air underneath the tile. Comb straight, parallel ridges instead.
Using Too Much Mortar Under Mosaic Tile
An oversized notch can push mortar through the numerous grout joints in a mosaic sheet.
Skipping Back Buttering When It Is Needed
Large format porcelain, natural stone and tiles with irregular backs commonly benefit from having mortar keyed into the back before installation.
Using Thinset to Fix a Bad Substrate
A larger trowel should not become your solution for a badly uneven wall or floor. Correct significant substrate problems before setting tile.
Allowing Mortar to Skin Over
Mortar that sits too long after being combed can begin to form a surface film. This can reduce mortar transfer even when you are using the correct trowel.
Mike Belk's Rule for Choosing a Tile Trowel
When someone asks me what size trowel they should use, I start with the tile dimensions, but I do not stop there.
I look at five things:
- How large is the tile?
- What does the back of the tile look like?
- How flat is the wall or floor?
- Is this a dry, wet or exterior installation?
- What does the mortar coverage look like when I lift a test tile?
That fifth question is what settles it for me.
If you have the proper mortar coverage without excessive mortar squeezing through the joints, your trowel size and technique are doing their job.
If you do not have the coverage you need, make the adjustment before continuing.
Bottom Line: Start With the Trowel Chart, Finish With a Coverage Check
If you came here asking, "What size trowel should I use for tile?" start with the tile trowel size chart near the top of this guide.
Then perform one more step before committing to the installation.
Pull a tile back up and look underneath it.
Your trowel should deposit enough mortar to achieve the proper coverage for your installation without leaving significant voids or forcing unnecessary amounts of mortar into the grout joints.
Key the mortar into the substrate, comb straight ridges, use the appropriate starting notch, back butter when needed and periodically check your coverage.
The trowel size gets you started. The mortar coverage tells you whether you chose correctly.
