Instantly calculate how many CMU concrete blocks, bags of mortar, and cubic yards of grout fill you need for any block wall — retaining walls, basement walls, garden walls, fence walls & more.
Enter your wall dimensions to calculate CMU blocks needed, mortar bags, fill volume & estimated cost.
Standard block: 1.125 blocks per sq ft of wall face. ~28 lbs each.
Total linear feet of wall
Standard 8" block = 8 courses per 5.33 ft of height
Full fill required for retaining walls over 4 ft and all structural walls
Calculator will subtract standard 3'×7' opening per count
A concrete block wall (also called a CMU wall — Concrete Masonry Unit) is one of the most widely used construction systems in the United States for foundations, basements, retaining walls, and commercial buildings. The standard US block size is 8 inches wide × 8 inches tall × 16 inches long, which with a 3/8" mortar joint produces a nominal 8"×8"×16" unit that lays up at exactly 1.125 blocks per square foot of wall face. The number of blocks you need depends on your wall's total square footage, the block size selected, the number of openings, and a waste factor for cuts and breakage — all of which this calculator handles automatically using formulas aligned with NCMA TEK standards and ACI 530 masonry design code.
A standard 8"×8"×16" CMU block with 3/8" mortar joints covers exactly 0.889 square feet of wall face per block, meaning you need 1.125 blocks per square foot. To find total blocks: multiply Wall Length (ft) × Wall Height (ft) × 1.125, then add your waste factor. Always add at least 10% for cuts, corners, and breakage — masonry suppliers typically do not accept returns on cut or damaged blocks.
The most widely used block in the USA. Weighs approximately 28 lbs, costs $2.00–$2.75 per block at Home Depot, Lowe's, or masonry supply yards. Used for basement walls, retaining walls, garden walls, and commercial construction. Meets ASTM C90 for load-bearing applications.
Used for below-grade foundation walls, heavy retaining walls, and structural commercial walls. Weighs approximately 45 lbs and costs $3.50–$5.00 per block. Provides greater lateral load resistance — required by most US building codes for basement walls over 7 ft tall that retain soil on one side.
Used for non-load-bearing interior partition walls, garden walls under 3 ft, and landscape features. Weighs approximately 21 lbs and costs $1.75–$2.25 per block. Lighter and easier to handle for DIY projects. Not recommended for retaining soil or structural applications without engineering review.
Calculating a concrete block wall requires three separate calculations: blocks needed, mortar bags required, and grout fill volume (if cores are filled). The formulas below are based on standard US masonry practice using 3/8" mortar joints and NCMA TEK 14-7B mortar usage guidelines.
In most US states, any retaining wall over 4 feet in height (measured from the bottom of the footing to the top of the wall) requires a building permit and stamped engineering drawings. The International Residential Code (IRC Section R404) requires reinforced CMU walls with filled and rebar-grouted cores for all walls retaining more than 4 feet of soil. Never build a retaining wall over 4 ft without consulting a licensed structural engineer — failure of an unreinforced retaining wall can cause serious injury and property damage.
The table below provides a quick-reference guide to how many blocks, mortar bags, and cubic yards of grout fill are needed per 100 square feet of wall face for each standard US CMU block size, based on 3/8" mortar joints and NCMA TEK guidelines.
| Block Size (W×H×L) | Blocks per 100 sq ft (+10%) | Mortar Bags per 100 sq ft | Grout Fill (Full Cores) | Block Cost / Unit (2026) | Best Application |
|---|---|---|---|---|---|
| 4" × 8" × 16" — Veneer | 124 blocks | 30 bags (60 lb) | 0.18 cu yd | $1.50–$2.00 | Non-structural veneer |
| 6" × 8" × 16" — Partition | 124 blocks | 33 bags (60 lb) | 0.24 cu yd | $1.75–$2.25 | Garden / partition walls |
| 8" × 8" × 16" — Standard | 124 blocks | 40 bags (60 lb) | 0.33 cu yd | $2.00–$2.75 | Retaining / basement walls |
| 8" × 4" × 16" — Half Height | 225 blocks | 45 bags (60 lb) | 0.33 cu yd | $1.50–$2.00 | Step courses / transitions |
| 12" × 8" × 16" — Heavy | 124 blocks | 44 bags (60 lb) | 0.55 cu yd | $3.50–$5.00 | Foundation / structural walls |
Building a strong, level CMU block wall the first time requires careful preparation and adherence to US masonry standards. Follow these best practices used by professional masons from coast to coast.
All CMU walls must rest on a concrete footing — never on soil. Per ACI 530 and IRC R403, the footing must be at least as wide as twice the wall thickness and extend below the frost line. In northern US states (MN, WI, NY), the frost depth can be 42"–60" — always check your local frost depth before pouring.
String a mason's line (chalk line) between corner leads before laying every course. This is the #1 technique professional masons use to keep courses straight, plumb, and level over long wall runs. Check every block with a level — a small error in the first course multiplies with every course above it.
Always use a running bond pattern — each block overlaps the joints below by half a block (8 inches). This is required by ACI 530 for structural masonry and provides maximum wall strength. Stack bond (joints aligned vertically) is only allowed for non-structural decorative walls with horizontal joint reinforcement every 16 inches.
Mortar should have a peanut butter consistency — it holds its shape when squeezed but doesn't crumble. Use Type S mortar (ASTM C270) for all below-grade and exterior US applications — it has higher strength (1,800 PSI) and better water resistance than Type N. Avoid adding too much water or the mortar bond will be weak.
For all retaining walls over 3 ft, basement walls, and any structural CMU wall in the USA, place #4 or #5 vertical rebar in filled cores per your engineer's schedule. Horizontal joint reinforcement (Dur-O-Wal or similar) every 16" (every 2 courses) adds tensile strength against cracking. Required by IBC Section 2104 for seismic and wind design.
All CMU walls below grade must be waterproofed per IRC R406. Apply a minimum of two coats of bituminous waterproofing (such as Tuff-N-Dri or Tremco Paraseal) on the positive side of the wall, plus a drainage board and gravel backfill. In high water table areas, install a footing drain (French drain) per IRC R405.
Concrete blocks are typically sold in cubes of 90 standard 8"×8"×16" blocks at masonry supply yards. Buying by the cube saves 15–25% vs. buying individual blocks at Home Depot or Lowe's. A cube of 90 standard CMU blocks typically costs $160–$220 at wholesale masonry supply yards in the USA. For projects requiring more than 200 blocks, always call your local masonry supply yard for cube pricing and delivery — most offer free delivery within 25 miles for orders over 10 cubes.
The cost of a concrete block wall in the USA depends on block size, wall height, whether cores are filled, labor costs in your region, and whether rebar and waterproofing are required. Below are realistic 2026 cost ranges for both DIY and contractor-built CMU walls.
A standard 6-ft tall, 20-ft long 8" CMU wall requires ~135 blocks + 54 mortar bags + fill. DIY material cost: approximately $350–$550 total including blocks (~$2.50 avg), mortar (~$7/bag), rebar, and gravel. Does not include footing concrete, tools, or waterproofing.
Professional masonry contractors in the USA charge $20–$45 per square foot for a standard 8" CMU wall fully installed, including footing, block, mortar, rebar, and grout fill. A 6-ft tall, 20-ft long wall (120 sq ft) would cost approximately $2,400–$5,400 installed depending on your region and wall complexity.
CMU blocks are available at Home Depot ($2.08–$2.68 per 8" block), Lowe's, Menards, and local masonry supply yards. For large projects, Oldcastle, CEMEX, and Quikrete block are the major US manufacturers. Always check local masonry supply yards first — they typically offer better pricing, cube delivery, and a wider range of specialty blocks.
Trusted US standards, NCMA guides, and masonry resources for CMU block wall design and construction.
The National Concrete Masonry Association (NCMA) TEK Manual is the definitive US reference for CMU block design, construction, and materials. Free TEK notes cover block specifications, mortar selection, retaining wall design, and code compliance for all US states.
View NCMA TEK NotesASTM C90 — Standard Specification for Loadbearing Concrete Masonry Units is the primary US specification for CMU blocks used in structural applications. Required by ACI 530 and specified on virtually all US commercial and residential masonry project drawings.
View ASTM C90Quikrete's official project guide for concrete block walls covers step-by-step DIY instructions for garden walls, retaining walls, and fence walls using standard CMU blocks and Quikrete mortar mixes — ideal for US homeowners tackling their first masonry project.
View Quikrete Block Guide