Concrete Block Calculator
Calculate how many concrete blocks, cinder blocks or CMU blocks you need for any wall. Get block count, mortar bags and fill concrete.
Wall Dimensions
Estimation Results
Concrete Block Formula
Standard 8×16 block = 0.889 sq ft of wall area per block
Blocks needed = Wall area ÷ 0.889
How Many Concrete Blocks Do I Need?
To determine how many blocks you need, first calculate your wall's surface area by multiplying the length by the height in feet. If you have any doors or windows, calculate their area and subtract it from your total wall area to get your net square footage.
Next, divide that net area by the coverage of a single block. A standard 8×16 inch concrete block covers exactly 0.889 square feet of wall space (this accounts for the standard 3/8-inch mortar joint). Finally, always add 10% to your final number to account for cut pieces, corners, and potential breakage on the job site.
Cinder Block vs Concrete Block vs CMU — What's the Difference?
When planning a masonry wall, you'll often hear the terms "cinder block," "concrete block," and "CMU" used interchangeably. While they essentially describe the same structural product used to build walls, the terminology reflects the history of how they were made. "Cinder block" is an informal, older term originating from when coal cinders and ash were used as the primary aggregate, making the blocks relatively light but less strong.
Today, modern blocks are manufactured using sand and fine gravel stone aggregates bound together with Portland cement. In the construction industry, these modern, high-strength units are technically referred to as Concrete Masonry Units (CMUs). Whether your blueprints call for CMUs, cinder blocks, or concrete blocks, the mathematical calculation to estimate them is identical.
Frequently Asked Questions
How many concrete blocks do I need for a wall?
Divide the total wall area (length × height in sq ft) by 0.889 for standard 8×16 inch blocks. Add 10% for waste and cuts.
How many cinder blocks per square foot?
Approximately 1.125 blocks per square foot of wall, or one block covers approximately 0.889 sq ft including mortar joints.
How much mortar do I need for a block wall?
A standard 60lb bag of mortar covers approximately 25 standard concrete blocks. Our calculator includes mortar bags in the output.
How do I fill concrete block cores?
For structural walls, fill cores with concrete and rebar. Use the fill toggle in the calculator to add cubic yards of fill concrete to your estimate.