Thinset Calculator

This thinset calculator will help you answer the question "How much thinset do I need?" for any sized tiling project. If you are still trying to figure out how many tiles you'll need for a tiling project, our tile calculator can help you with that.

Using this tool, you will learn what thinset is, as well as the basics of how to mix thinset. You will also find out how to distinguish thinset vs. mortar when mixing cement and sand. Keep on reading to learn more.

Thinset is an adhesive compound used to install materials, like tiles and bricks, onto substrates, like walls and floors. Thinset is a mixture of cement and sand, with some additives and polymers that make the mixture more flexible, workable, and adhesive.

How to mix thinset is very similar to how you mix mortar. However, you can now find dry pre-mixed thinset that needs only water to get activated. Thinset comes in two general types: the unmodified thinset and the modified thinset. The main difference between the two is the presence of polymers, usually latex, in the modified thinset.

Due to the presence of latex, modified thinset needs to dry well to set properly, and thus it is perfect for installing tiles onto concrete and plywood. Concrete and plywood can help the modified thinset dry faster by absorbing some of the water in the thinset mix.

On the other hand, like concrete, unmodified thinset cures stronger in the presence of moisture. For this reason, tile installers prefer using unmodified thinset on surfaces with membrane-type waterproofing materials. These materials do not absorb water, and the trade-off is that the thinset takes a little longer to cure. Nevertheless, you can always refer to the packaging of the thinset to know what thinset is best for your project.

In this thinset calculator, we focus on determining the volume and weight of the thinset required while considering the size of the tiles to be installed and the typical density of the thinset.

How much thinset you need depends on the total area of your project and the size of tile you wish to install. Larger tiles need thicker thinset to support the tiles, while smaller tiles can get away with a thinner thinset to secure them. To achieve a consistent thickness throughout an area, we can use a notched trowel that leaves a uniform set of thinset beads across the substrate.

The notch size of the trowel defines the size of the beads it produces. When installing the tiles, these beads get squished flat and decrease the chances of trapped air between the tiles and the substrate. You can use the table below as a guide on what trowel size and thinset thickness you should use for specific tile sizes:

There are other notch shapes and sizes available on the market today, but these are the most common ones in use. As you can see from the table, the smaller trowel sizes provide thinner thinset thicknesses for smaller tiles, while the larger trowel sizes provide thicker thinset for larger tiles.

Here are the steps you can follow to use our thinset calculator to find out how much thinset you need:

1. Enter the length and width of the area you are working on. However, if you already know your area, you can also input the number directly into the Total area to be tiled field.

2. Choose the tile size you are going to use. This will generate the maximum thinset thickness suitable for your tile to ensure that you will get sufficient adhesion to your tiles. You can also enter your preferred thinset thickness if you wish to do so.

3. Our thinset calculator will provide you with the thinset volume and the number of bags of dry thinset needed for your project. As you can see, we have predetermined the values for wastage and weight per bag, but you can change them depending on your situation.

4. If you wish to change the density of the thinset, you can do so by going to the advanced mode of our thinset calculator. There you can also modify the dry material percentage of your thinset mix. By default, this is set to 50%, which means that the amount of water and dry thinset is in a 1:1 ratio.

To find the amount of thinset by volume, we need to multiply the total area of the substrate on which we are going to install our tiles by the thinset thickness needed to fix the tiles in place, as shown in the equation below:

where:

• $V_\text{t}$ – Volume of thinset;
• $A_\text{s}$ – Area of substrate; and
• $T_\text{t}$ – Thinset thickness.

For the thinset thickness, please refer to the table we provided in one of the previous sections. Though we can also choose to apply thick thinset for smaller tiles, it would still be best to use only what is needed to minimize expenses.

Let's say we want to install 8" square tiles on a 6 square meter area and have chosen (from the table) a 4.0 mm for the thinset thickness (or 0.004 m). We can calculate the volume of thinset needed, as shown below:

After determining the thinset volume, we need to multiply it by the thinset density, we denote below as $\small \rho_\text{t}$, which is typically $\small 12,\!162\ \text{kg/m}^3$, or approximately $\small 135\ \text{lb/ft}^3$.

It is also best to incorporate the amount of wastage now. For our example, let's say we want to assume a wastage of 10%, we can now find the weight of thinset, $\small W_\text{t}$, needed, as shown in this calculation:

We can now say that we would need 57 kg of thinset mixture for our small tiling project from our sample calculations above. To calculate how much dry thinset we would need for our project, we need to determine how much water is in the mixture and subtract it from this weight.

Typically, we mix thinset in a 1:1 ratio which means that we mix the same weight of dry thinset and water. With that said, for the 56-kg thinset mix, we need to mix 28.5 kg of water and 28.5 kg of dry thinset. For this project, we could buy two 20-kg bags of dry thinset or, if available, one 30-kg bag of dry thinset.

When installing tiles, we also usually install them with gaps between each other and fill these gaps with grout for a number of reasons. To learn about these reasons, you can check them out in our grout calculator.