Michael F. answered • 09/09/19
B.S. from UI, #1 Engineering School. 100's hrs. tutoring.
Concrete building blocks are made of a porous, lightweight form of concrete... normally concrete has a density of about 150 lbs. per cubic foot, but concrete block density is much lower. Of course the blocks have channels in them so they are not monolithic. If you needed to calculate the volume empirically, you would do it as Archimedes did, by water displacement. Then calculate the weight based on the density of that particular type or brand of concrete block. Most blocks have a known weight based on their size or brand. You would normally look that up from the manufacturer, and then multiply by the number of units needed. OF course in the constructed wall they will also be filled with concrete and reinforcement bars. These elements would have to be added up, or there may be unit weights per square yard of finished wall available on tables.
