Concrete Block Calculator
Count concrete blocks (CMU) for a wall.
Enter your wall length and height to get the number of standard concrete blocks (CMU) needed, including a waste allowance for breakage and cuts. The estimate uses the common rule of about 1.125 blocks per square foot of wall for a standard 8×8×16-inch block with mortar joints.
How it works
A standard CMU block faces about 16 by 8 inches. With a 3/8-inch mortar joint, roughly 1.125 blocks cover one square foot of wall. Multiply the wall area by 1.125, add waste, and round up. Don't forget separate estimates for any double-thickness sections or pilasters.
Frequently asked questions
How many concrete blocks do I need?
Multiply wall length by height for the area, then by about 1.125 blocks per square foot, and add waste. A 20×8 ft wall needs roughly 189 blocks with 5% waste.
How many blocks are in a square foot of wall?
About 1.125 standard 8×8×16-inch blocks per square foot, allowing for the mortar joints.
How much waste should I add for block?
Around 5% for breakage and cuts on a straight wall. Add more for walls with many corners or openings.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.