How to estimate mortar for a block wall

Written by shellie braeuner Google
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How to estimate mortar for a block wall
Mortar can give concrete block eye appeal as well as hold the wall together. (cold concrete blocks image by jbattx from

Stopping in the middle of a project to get more supplies is frustrating--almost as frustrating as throwing away supplies because you mixed too much. A seasoned mason can look at a project and tell almost exactly how much mortar to purchase and mix. However, the rest of us need a little help. Estimating the correct amount of mortar isn't difficult and it will save you time and money in the long run.

Skill level:

Things you need

  • Tape measure
  • Calculator

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  1. 1

    Measure the length of the projected wall and estimate the planned height.

  2. 2

    Multiply the length by the height in feet. This will give you the area of the project in square feet. For example, a 26-foot wall that is 5 feet high would contain 130 square feet of surface.

  3. 3

    Calculate the ratio of mortar needed. According to builders and concrete suppliers, it takes about 3 cubic feet of mortar for every 100 feet of wall. This can be rendered mathematically as 0.03.

  4. 4

    Multiply the area of the wall by the ratio; in this example 130 x 0.03 = 3.9. So a wall 26 feet long and 5 feet tall would require almost 4 cubic feet of mortar.

Tips and warnings

  • There are special masonry calculators, such as the one at, that help you determine the necessary supplies. You plug in the length and height of the wall as well as the size of the block, and the calculator will tell you how many blocks and how much mortar are needed for the project.
  • This is an estimate. Smaller blocks will need a little more mortar, while larger blocks need a little less.

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