Concrete Block / CMU Calculator
Calculate how many concrete masonry units (CMU) you need for your wall, along with mortar bags and rebar. This calculator supports standard 8×8×16, half-height 8×4×16, and 8×8×12 block sizes with adjustable mortar joint thickness.
Enter Your Wall Dimensions
Full Breakdown
Wall Area
Block Size
Courses (Rows)
Blocks (Exact)
Blocks (w/ 5% Waste)
Mortar
Rebar
How to Use This Calculator
- Enter the wall length and height in feet.
- Select the block size — standard 8×8×16 is most common for structural walls.
- Choose your mortar joint thickness (⅜" is standard).
- Click "Calculate Blocks" for a complete material list.
- Results include 5% waste factor and rebar estimates for every 4 feet.
The Formula
For standard 8×8×16 blocks with ⅜" mortar joints:
Blocks per sq ft = 1 ÷ ((Block Height + Joint) × (Block Width + Joint)) in sq ft
Standard: ~1.125 blocks per sq ft of wall face
Mortar: approximately 3.5 bags (70 lb) per 100 blocks.
Rebar: vertical bars every 4 feet plus horizontal reinforcement every 4 feet of height.