CMU Wall Design Calculator

This calculator takes off CMU (concrete masonry unit) block wall quantities -- blocks required, vertical rebar bars, grout volume, and mortar bags -- built around a fixed nominal 16-inch by 8-inch block regardless of what Block Width is set to. Wall Height and Wall Length both drive Blocks Required together: the wall is divided into rows by height and blocks per row by length, those two counts multiply, and the result is reduced by whatever Openings Area is entered for doors and windows. Block Width, despite being a genuinely important structural parameter for load-bearing capacity in real construction, only touches the grout calculation here -- it looks up an estimated cubic feet of grout per cell for 8, 10, or 12-inch block, falling back to the 8-inch figure for anything else, and Blocks Required never changes no matter what width is entered.

Vertical Rebar Spacing sets Vertical Rebar Bars by dividing Wall Length by that spacing, and by default it also determines how many cells get grouted each course, unless Grouted Cells Override is set to a specific number instead. Mortar Bags scales with Blocks Required at a fixed rate of 3 bags per 100 blocks. Consult a licensed structural engineer before finalizing a load-bearing CMU wall design.