ft
Enter lengthft
Enter heightft²
$
Cement Blocks Needed
—
Was this calculator helpful?
How to Calculate Cement Blocks
Standard 8×8×16 CMU blocks have a nominal face area of 0.888 ft² (including the 3/8" mortar joint). Divide net wall area by the block face area, then add waste.
Net Area = (Length × Height) − Openings
Blocks = (Net Area ÷ Block Face Area) × (1 + Waste%)
Mortar: approx. 1 bag (70 lb) per 30–35 standard blocks. Pallets: 90 blocks per standard pallet of 8×8×16.
💡 Pro tip: Standard CMU uses 3/8" mortar joints. For retaining walls, add #4 rebar every 4 ft horizontally and at corners, and fill cores with grout.
FAQ
Installed cost is typically $10–$20 per sq ft. A 30×8 ft wall (240 ft²) runs $2,400–$4,800 installed. Materials alone (blocks + mortar) are roughly $3–$6/ft².
A standard pallet of 8×8×16 blocks holds 90 blocks. Order in full pallets where possible to minimize cost and delivery fees.
Structural and retaining walls over 3 ft require a concrete footing — typically twice the wall width, depth to frost line. Garden walls under 3 ft may use a compacted gravel base. Always check local building codes.
CMU (Concrete Masonry Unit) is made with Portland cement and aggregate — it is the modern standard, strong and uniform. True cinder blocks used fly ash (coal byproduct) as aggregate and are no longer widely produced. The terms are used interchangeably in the field, but modern "cinder blocks" at building supply stores are actually CMU. CMU is stronger, more uniform in size, and ASTM-compliant. Use CMU for any structural application.
Installed CMU wall cost ranges from $10–$25 per square foot depending on wall type, height, reinforcement, and region. A simple 8-inch CMU garden wall runs $10–$15/ft². A reinforced retaining wall with rebar and grouted cores runs $15–$25+/ft². Labor typically accounts for 50–60% of total cost. DIY masonry is possible but requires practice — consider hiring for structural or retaining walls where errors are costly.
Rebar and grout-filled cores are required for: retaining walls (especially over 3 ft), seismic zones (most of the US to some degree), structural load-bearing walls, and anywhere local code requires reinforced masonry. Typical reinforcement: #4 rebar vertically every 4 ft and at corners, #4 rebar horizontally every other course or at top and bottom, all filled cores grouted solid. Always consult local building code for your specific application.
Related Calculators