How to Calculate the Amount of Mortar Mix Needed

Mortar plays a critical role in masonry construction, serving as a form of adhesive to join brick and block. Running out of mortar mix after you've started your project can affect both your schedule and the quality of your work, while stocking up on too much mortar is a waste of money. Before you begin laying brick or block, calculate how many bags of mortar mix you'll need based on the size and scope of your project.

Brick Wall
credit: Gudella/iStock/Getty Images
White mortar contrasts with a red brick wall.

Mortar Mix for Brick

Step 1

Find the area of your brick structure by multiplying length and width. If the structure has more than one side, add the area of each side together to find total area in square feet. For example, a wall measuring 10 feet wide by 10 feet high has an area of 100 square feet.

Step 2

Multiply the square footage by seven to estimate the number of bricks you use in your project. A 100-square-foot wall will require approximately 700 bricks.

Step 3

Divide the total number of bricks by 30 to estimate how many 60-pound bags of mortar mix you need. For a wall constructed with 700 bricks, you need 23.33 bags of mortar. Round this figure up to the nearest whole number before making your purchase.

Mortar Mix for Concrete Block

Step 1

Find the area of your block structure by multiplying the width times the height. A wall measuring 10 feet by 10 feet has an area of 100 square feet, for example.

Step 2

Multiply the square footage of your block structure by 1.125 to find out how many blocks you need. For a 100-square-foot wall, you need 112.5 blocks.

Step 3

Divide the number of blocks in your project by 11 to discover how many 60-pound bags of mortar mix you need to purchase. A wall built using 112.5 blocks requires 10.23 bags. Round this number up to the nearest whole number before making your purchase.