It's natural for a certain kind of mind to wonder how many bricks or blocks are in a wall. The simplest and surest way to obtain that number, of course, is to count them all, but that could take a long time, and it isn't of any help to someone who wants to know how many blocks are needed to build a wall that isn't there yet. Fortunately, basic arithmetic can be used to calculate a fairly reliable estimate to satisfy curiosity as well as practicality.
Determine the dimensions of the wall in question. If it's an actual wall or the physical site where you intend to build one, you may need to measure it with measuring tape. If there is already an architectural plan on paper for the wall, you should be able to obtain the dimensions from that.
Calculate the surface area of the wall, using the dimensions obtained in Step 1. For a simple rectangular wall, this will just be the height times the length. More complex shapes, with curved or angled edges or windows, may call for more sophisticated skills in geometry.
Measure the height and length of a single concrete block, and include the thickness of one layer of mortar. (Although all four edges of the block will usually have a layer of mortar, the total surface area each block accounts for should only include one layer for height and one for width, since the adjacent blocks will account for the other layers.) Be sure to use the same units that you used to measure the wall. For example, if you measured the wall in feet, measure the block in feet.
Calculate the surface area of a single block in the wall, including its mortar allowance. For example, if your standard concrete block is 1 foot by 0.5 feet and is separated from its neighbours by a half-inch of mortar, then each block accounts for 1.0417 x 0.5417, or 0.5643 square feet.
Divide the total surface area of the wall by the surface area of the representative block to get the total number of blocks in the wall.