Whether you are planning a small backyard construction project or you are aspiring to build the next wonder of the world, our mortar calculator should be one of your starting tools to use.

Even the most straightforward construction projects require at least some sort of planning. And if you are working with bricks and mortar, it is always good to exactly know beforehand how much of the material you’ll need. 

With this calculator, you can calculate an approximate amount of mortar needed for the given number of bricks that you are planning to use. 

Here, we will explain how the mortar calculator works, the exact math formula behind the calculator and how to use it and read the results. 

What is mortar?

Next to bricks and blocks, mortar is one of the most widely used construction materials. There are various types of mortar, but its purpose is always the same. We use it to bind bricks, stones, concrete blocks, or other construction materials to form a stable and steady structure. 

Essentially, mortar is a balanced mixture of cement, sand and water that acts like glue holding other construction materials (like blocks and bricks) together once it dries out.

Nowadays, you don’t have to make a mixture of cement and sand on your own to make mortar. Instead, you can buy it ready-made in your local hardware shop. Check this Sand Calculator to learn more about it.

The mixture ratio of cement and sand in mortar is usually around 1:4, which means that a standard 80 lb. (36,2 kg) bag of mortar contains 4/5 of sand and 1/5 of cement mixed.

What is the yield of a mortar bag?

One of the most important things to know before using our mortar calculator is the yield per bag of mortar

After mixing up with water, the yield of a mortar bag is essentially the surface of the area that we can effectively cover with one bag of mortar. We usually express this in square feet or square meters.

For example, one standard 80 lb. (36,2 kg) bag of mortar can lay up to 40 standard-sized bricks or effectively cover around 24 square feet of the surface.

We can also express the yield of a mortar bag in cubic feet, one standard 80 lb. bag of premixed mortar will yield approximately 0.7 cubic feet of wet mortar after mixing up with water.

However, as you might already know, not all the bricks/blocks are the same size, and the yield of a mortar bag depends on the type of bricks/blocks used. 

Sometimes, the producer writes the yield per bag of mortar on the bag itself as part of the product specification, so you might want to check if this is the case for the type of mortar you are planning to use.

Unfortunately, this is not always the case. So we came up with this table where you can find the approximate yield per bag of mortar for different standard sizes of bricks/blocks.

To make it easier and more appropriate with our mortar calculator, we expressed the yield per bag of mortar as the number of bricks it can lay.

Brick/block size80 lb (36.2 kg bag)
Modular bricks40
Queen size bricks35
King size bricks30
Utility bricks25
4 inch blocks15
6 inch blocks12
8 inch blocks10
10 inch blocks10
12 inch blocks9

Note that we calculated the yields in the given table without considering any amount of waste.

But, of course, this is practically almost impossible to achieve. Thus, the amount of mortar you need is always slightly higher than the value in the table.

How to use the mortar calculator?

The calculator will help you determine how much mortar you need for the given amount of bricks you plan to use for your construction project.

Step 1: Select between bricks and blocks

Bricks and blocks are the most common construction materials bound together with mortar. However, the standard sizes of bricks are different from the standard sizes of the blocks. 

Therefore the first step when using our calculator is to select whether you want to calculate bricks or blocks.

You can do this within the first field of the calculator named ‘Calculate mortar for:’ On the right side of the given field, you can select either bricks or blocks from a drop-down menu.

Step 2: Input the number of bricks/blocks

Assuming you have already calculated the number of bricks/blocks you’ll need for whatever you are building, the next step is to input the number of bricks/blocks you plan to use. 

Step 3: Enter the correct value of yield of one mortar bag

You can do this by checking the table above, where you can find values for yield per bag of mortar for different sizes of bricks/blocks.

Step 4: Reading the final score

Once you input the number of bricks/blocks and the yield value per bag of mortar, you will instantly see how many bags of mortar you’ll need for your project.

Also, there is the ‘Single bag’s weight’ field at the bottom that you can use to calculate the amount of needed mortar in pounds or kilograms. So, to calculate this, you’ll need to know the total weight of one bag of mortar that you are using. 

Once you input the weight value in the ‘Single bag’s weight‘ field, you will instantly get the value of the total weight of premix mortar that you’ll need.

Note that the final score is a round number.

If you need a more precise result, you can get it by right-clicking on the ‘Mortar bags’ field and then selecting the ‘Show solution‘ option. You will get the exact amount of mortar at the bottom.

For example, if we want to use 90 bricks and the value of yield per bag of mortar is 40, if we enter these amounts into the calculator, we will get the round number, i.e. the calculator will show that we need three bags of mortar. 

However, if you right-click on the ‘Mortar bags field‘, you will see that the exact amount of mortar we need is 2.25 bags, and you will also see the formula used to get this value.

The mortar calculator formula

As you can see, the math behind the mortar calculator is pretty simple once you know the value of yield per bag of mortar and the number of bricks and blocks you are planning to use.

Essentially the calculator divides the number of bricks/blocks with the value of yield per bag of mortar so, if you are wondering, the formula behind the calculator is:

\frac{Number \hspace{1.5 mm}of\hspace{1.5 mm} bricks/blocks }{Yield\hspace{1.5 mm} per\hspace{1.5 mm} bag}  = Number\hspace{1.5 mm} of\hspace{1.5 mm} bags\hspace{1.5 mm} of mortar

Let’s see how this works with a real-world example.

Let’s say that we decided to build a wall, and we know that we need 1200 standard-sized bricks for the construction. 

We also know from the table above that the yield per bag of mortar is 40.

  • The total number of bricks used is 1200
  • The yield per bag is 40 (one bag of mortar can lay around 40 bricks)

If we apply the mortar calculator formula, we will have:

\frac{1200\hspace{1.5 mm}bricks}{40\hspace{1.5 mm}(yield\hspace{1.5 mm} per\hspace{1.5 mm} bag)}= 30

So, to lay 1200 bricks, we will need approximately 30 bags of premix mortar.

FAQ

How do you calculate wall mortar?

As explained above, to calculate how many bags of wall mortar you need for your wall construction, you need to determine the approximate yield per bag of premix mortar. 

A standard 80 lb bag of mortar will yield approximately 0.7 cubic feet of wet mortar and lay around 40 standard-sized bricks. 

You can use the table provided above as a reference.

Once you know the yield per bag of mortar you plan to use, you’ll also need to know how many bricks you will use to construct the wall.

To calculate the total amount of bags of mortar needed for your wall, you can divide the number of bricks by the yield of a bag of a mortar expressed as the number of bricks it can lay.

How do you calculate sand and cement for mortar?

Usually, mortar comes as a premix mass of cement and sand in a ratio of 1:4. So, for each measure of cement, there are four measures of sand. Therefore, we can conclude that premix mortar usually contains ⅕ of cement and ⅘ of sand.

For example, if you want to make 5 kilograms of mortar on your own, you would need to mix 1 kilogram of cement with 4 kilograms of sand.

What is the difference between mortar and concrete?

Even though they consist of similar ingredients (and look very similar), they are still significantly different construction materials. 

Mortar is a mixture of cement and sand, while concrete is also a mixture of cement and sand, but it also contains gravel, a material that is a kind of crushed stone that makes concrete structures stronger. 

Also, a wet mixture of mortar contains more water than a wet mixture of concrete.

Summary

We hope you found this calculator helpful, and we hope that you were also able to understand better the way it works and how to use it after reading this article. We are constantly adding new calculators, so feel free to check back again soon for more relevant calculators to help you with construction projects.

Here are also some other calculators that you might find helpful for your construction projects: Roofing Calculator, Roof Pitch Calculator, Square Footage Calculator