How many concrete blocks do I need for a wall?

Divide the wall area in square feet by 0.89 (the face area of a standard 8×8×16 block including a 3/8-inch mortar joint). A 20 ft long, 8 ft tall wall is 160 sq ft ÷ 0.89 = 180 blocks. Add 5 to 10 percent for cuts and breakage, so plan for 190 to 200 blocks. Our calculator handles this math automatically and supports the three most common block sizes.

How much mortar do I need for concrete blocks?

A typical 8×8×16 CMU wall requires about 8 cubic feet of mortar per 100 blocks (assuming 3/8-inch face shell bedding joints). For 1,000 blocks, that is roughly 80 cubic feet, or about 3 cubic yards (a cubic yard is 27 cubic feet). Type N mortar is the standard for above-grade walls; Type S is required for below-grade or load-bearing walls. One 80-lb bag of pre-mix mortar yields about 0.6 cubic feet, so 1,000 blocks need around 135 bags.

What sizes of concrete block are available?

The three most common CMU sizes are 8×8×16 (standard structural block, 0.89 sq ft face area with mortar joint), 8×12×16 (extra-thick walls, retaining walls, foundations), and 4×8×16 (partition or non-structural interior walls). Half-blocks, corner blocks, and bond-beam blocks are also available for specific structural details. Lintel blocks have a U-shape to receive rebar over openings.

How much does a concrete block cost in 2026?

A standard 8×8×16 CMU block costs $1.50 to $3.00 each at home centers and masonry suppliers. Larger 8×12×16 blocks run $2.50 to $4.50 each. Decorative or split-face blocks can hit $4 to $8. Mortar adds $5 to $7 per 80-lb bag, rebar adds $0.50 to $1 per linear foot for #4 (1/2-inch) bar, and professional labor for installed block walls runs $9 to $14 per square foot for standard work, up to $20 per square foot for retaining walls with reinforcement.

Do I need rebar in a concrete block wall?

Yes for almost every structural application. The International Residential Code (IRC) requires vertical rebar at corners and at maximum 4-foot intervals in CMU walls used for foundations or load-bearing applications, plus horizontal joint reinforcement (ladder or truss wire) every other course. Retaining walls over 4 feet typically require engineered rebar plans, vertical bars in every cell, and grouted cells at minimum 32 inches on center.

Can I lay concrete blocks myself?

Small non-structural projects (a 4-foot garden retaining wall or a low planter box) are reasonable DIY projects with patience and basic masonry tools. However, foundation walls, structural walls, and any retaining wall over 4 feet should be done by a licensed mason or under engineering supervision. Mistakes in plumb, level, or rebar placement can produce expensive structural failures down the road.

How do I calculate fill grout for concrete blocks?

Each 8×8×16 CMU has two cells with a combined volume of about 0.18 cubic feet per block. If you fill every cell, 100 blocks need 18 cubic feet of grout (about 5 cubic yards per 1,000 blocks). For walls grouted only at vertical reinforcement intervals (every 32 or 48 inches on center), divide accordingly — typically only 25 to 33 percent of cells are filled. Use a fluid-consistency grout (8 to 11 inch slump) so it flows around the rebar without voids.

How long does a concrete block wall last?

Properly built CMU walls easily last 80 to 100+ years. Failure modes are usually water intrusion (causing efflorescence and freeze-thaw spalling), missing rebar in retaining applications, or settlement from inadequate footings. A penetrating silane sealer applied every 7 to 10 years dramatically extends the surface life of exposed block. The Portland Cement Association reports that documented CMU foundations have lasted over 100 years with minimal maintenance in moderate climates.

Concrete Block Calculator

Calculate exactly how many concrete (CMU) blocks, mortar bags, fill grout and rebar you need for any wall — with 2026 cost estimates.

Wall Dimensions

Wall Length (ft)

Wall Height (ft)

Block Type

Block Size8×8×16 = standard. 8×12×16 = retaining/foundation. 4×8×16 = interior partition.

Options

Waste Factor (%)

Cost per Block ($)Range: $2–$3

Cell Fill (Grout)

Partial = vertical reinforcement at 32" o.c. Full = every cell grouted (max strength)

Blocks Needed

189 blocks

160 sq ft wall · 5% waste included

Mortar (cu yd)

0.56 yd³

26 bags of 80-lb pre-mix

Fill Grout

0.38 yd³

Partial fill

Rebar (#4)

60 ft

Vertical + horizontal

Materials Cost

$702

Blocks + mortar + grout + rebar

Labor (Pro)

$1,760

~$11/sq ft installed

Total Installed

$2,462

Materials + labor

Tip

For retaining walls over 4 ft tall, consult a structural engineer — most jurisdictions require stamped drawings and full-cell grouting with continuous rebar.

How to Calculate Concrete Blocks

The formula for any block wall is simple: (wall length in feet × wall height in feet) ÷ block face area in square feet = blocks needed. The face area of a standard 8×8×16 inch CMU block, including a 3/8-inch mortar joint on all sides, is 0.89 square feet. A wall that is 20 feet long and 8 feet tall has 160 square feet of face area, requiring 160 ÷ 0.89 = 180 blocks before waste. Add 5 to 10 percent for cuts and breakage to land on a final order quantity.

Mortar requirements depend on the block size and joint thickness. The Portland Cement Association publishes standard mortar yields: 8 cubic feet per 100 blocks for 8×8×16 with 3/8-inch joints, 10 cubic feet for 8×12×16, and 5 cubic feet for 4×8×16 partition blocks. Pre-mixed Type N or Type S mortar is sold in 80-lb bags that yield approximately 0.6 cubic feet each, so 100 standard CMU blocks need about 14 bags.

For walls that require structural reinforcement, fill grout is poured into the cells around vertical rebar. A standard 8×8×16 block has two open cells with a combined volume of about 0.18 cubic feet. If every cell is grouted, 1,000 blocks need about 6.7 cubic yards of grout. Most residential walls fill only every other cell or every fourth cell at 32 inches on center, reducing grout volume by 70 to 75 percent. Use our concrete calculator to dial in cubic yards for the footing.

Concrete Block Cost in 2026

Block Type	Cost Each	Best For
8×8×16 standard CMU	$1.50 – $3.00	Foundations, walls, garden walls
8×12×16 thick CMU	$2.50 – $4.50	Retaining walls, basement walls
4×8×16 partition	$1.20 – $2.50	Interior non-load-bearing walls
Split-face decorative	$3.50 – $7.00	Architectural visible walls
Lintel block (U-shape)	$3.00 – $6.00	Headers over openings
Bond beam block	$3.50 – $6.50	Top course w/ continuous rebar

Mortar adds $5 to $7 per 80-lb bag of Type N or Type S pre-mix, and ready-mix grout for cell fill runs $130 to $180 per cubic yard delivered. Rebar (#4 grade 60) costs $0.50 to $1.00 per linear foot at home centers; quantity discounts apply at masonry suppliers. Professional installation labor averages $9 to $14 per square foot for standard CMU walls and rises to $18 to $22 per square foot for engineered retaining walls with full reinforcement.

Common Mistakes

Inadequate footing. CMU walls require a continuous concrete footing at least 16 inches wide and 8 inches deep, extended below the local frost line. Skipping this is the #1 cause of premature wall failure.
Skipping rebar in retaining walls. Even a 3-foot retaining wall holding back saturated soil exerts enough lateral pressure to crack ungrouted CMU. Always include vertical rebar tied into the footing.
Wrong mortar type. Type N (medium strength) is for above-grade non-load-bearing applications. Type S (high strength) is required for below-grade or load-bearing walls.
Forgetting joint reinforcement. Horizontal ladder or truss wire in every other course (16 inches o.c.) prevents shrinkage cracks and is required by most building codes.
No waterproofing. Below-grade CMU must have a waterproof coating (asphalt, rubberized membrane, or crystalline waterproofer) on the exterior face plus a perimeter drain at the footing.

CMU Industry Statistics 2026

2.5B

concrete masonry units produced in the U.S. in 2024 — second-largest construction material by volume after concrete (NCMA, 2025)

$6.4B

U.S. concrete block manufacturing market 2025 — concentrated in Texas, Florida, and California where slab-on-grade construction dominates (IBIS World, 2025)

100+

years lifespan documented for properly built CMU foundations — comparable to or exceeding poured concrete (Portland Cement Association, 2024)

Concrete block walls cost 20 to 30 percent less per square foot than poured-in-place concrete walls for residential applications, while delivering equivalent or superior compressive strength when properly grouted and reinforced (NCMA TEK Manual 2025). For complete project scoping, combine our CMU calculator with the concrete calculator for footings, the gravel calculator for drainage base, and the brick calculator if you plan to add a brick veneer face. Finance large block-wall projects through Amortio.