Concrete Block Calculator
Calculate the number of concrete blocks (CMU) needed for your wall. Enter wall dimensions, block size, and openings to estimate materials and costs.
Standard blocks are most common for walls
Total area of doors, windows, etc. (same unit as wall)
How many concrete blocks do I need for a wall?
For a standard 8"×8"×16" block with 3/8" mortar joints, you need approximately 1.125 blocks per square foot of wall. Calculate your wall area (length × height - openings) and multiply by 1.125, then add 10% for waste.
What is the most common concrete block size?
The standard concrete block (CMU) is 8"×8"×16" (nominal). Actual dimensions are typically 7-5/8"×7-5/8"×15-5/8" to allow for 3/8" mortar joints. This is the most common size for residential and commercial construction.
How much mortar do I need per block?
You need approximately 0.028 cubic feet of mortar per standard 8"×8"×16" block. An 80-pound bag of mortar mix covers about 0.75 cubic feet, or roughly 27 blocks. Always order extra for waste and thickness variations.
Should I account for waste when ordering blocks?
Yes, always add 5-15% extra blocks for waste, breakage, and cuts. 10% is standard for most projects. Complex layouts with many cuts or corners may need 15%. This ensures you don't run short mid-project.