How Many Blocks to Build a Wall?
To build a wall with standard 8x8x16 concrete blocks, multiply the wall's length in feet by 0.75, then multiply by the number of courses, one course for every 8 inches of height. A 20 foot long, 6 foot tall wall, for example, needs about 135 blocks before waste. Below is the full formula, a block count table by wall height, 2026 material and labor costs, and how a block wall compares to pouring concrete.
Key takeaways
- Blocks = wall length (ft) x 0.75 x courses, where courses equal height in inches divided by 8. Add 5 to 10% for waste.
- A 20 ft long, 6 ft tall wall needs about 135 blocks before waste, or 149 with a 10% allowance.
- 1,000 standard 8x8x16 blocks cost roughly 1,300 to 2,900 dollars for materials in 2026.
- A block wall runs about 12 to 20 dollars per square foot installed, cheaper than a poured wall at 18 to 40 dollars.
- The 0.75 blocks-per-linear-foot rate holds for any standard block width, 4 through 12 inches nominal.
How many blocks to build a wall: courses and length
To build a wall, multiply the wall's length in feet by 0.75, since a 16 inch block plus a 3/8 inch mortar joint covers 1.33 linear feet, and 1 divided by 1.33 is 0.75. Then multiply by the number of courses, since each course of standard block adds 8 inches of height.
This gives the same result as multiplying wall area by 1.125 blocks per square foot, but counting by courses matches how you actually build a wall, one row at a time, rather than by an abstract area.
Courses = Height(in) ÷ 8Blocks = Length(ft) x 0.75 x Courses x (1 + Waste% ÷ 100)Round every course up to a whole block, cut blocks belong at corners and openings, not mid run. For the exact count on your footprint, including openings, the concrete block calculator does the course by course math for you.
Blocks needed by wall length and height
Here is how the block count grows for a straight 20 foot wall run as it climbs in height, using standard 8x8x16 block, a 3/8 inch joint, and a 10% waste allowance for cuts and breakage.
| Wall height | Courses | Blocks (20 ft run, +10%) | Mortar bags (80 lb) |
|---|---|---|---|
| 2 ft | 3 | 50 | 4 |
| 4 ft | 6 | 99 | 8 |
| 6 ft | 9 | 149 | 12 |
| 8 ft | 12 | 198 | 17 |
Doubling the height roughly doubles the block count, since each added course runs the full length again. A short garden wall and a tall privacy or foundation wall on the same footprint are very different orders.
For a wall that is not one straight run, or that has door and window openings to subtract, break it into sections first. The block count by area guide covers openings, corners, and odd shapes in more detail.
Cost to build a block wall in 2026
Standard hollow 8x8x16 CMU costs about 1.25 to 2.50 dollars per block in 2026, or 150 to 330 dollars per pallet of 90. At that rate, 1,000 concrete blocks run roughly 1,300 to 2,900 dollars for materials, before delivery, pallet deposits, mortar, and any rebar or grout.
Add mortar at about 8 to 10 bags of pre-mixed 80 lb mix per 100 blocks, at roughly 7 to 10 dollars a bag, and the material total for a mid-size wall climbs by another 10 to 15%.
Labor roughly doubles the price. A finished block wall, materials and installation together, runs about 12 to 20 dollars per square foot in 2026, more for grouted, reinforced, or split-face block.
Poured concrete wall vs block wall: which is cheaper
Block is normally the cheaper way to build a wall. A standard block wall runs about 12 to 20 dollars per square foot installed, while a formed, poured concrete wall runs about 18 to 40 dollars per square foot, since poured walls need forms, more concrete volume, and more labor hours to set up and strip.
Poured concrete wins on strength for anything resisting heavy lateral load, like a tall basement wall holding back saturated soil, because it cures as one continuous, joint-free section. A block wall can match that strength, but only when the cores are fully grouted and reinforced with vertical rebar at the spacing an engineer specifies, which narrows the price gap.
For garden walls, property line walls, and most retaining walls under about 4 feet, block is the practical choice: cheaper, faster to build in stages, and easy for one or two people to lay without hired equipment.
Step by step: building a block wall from footing to cap
Start below the frost line with a poured concrete footing, generally at least twice the wall's width and never under 12 inches, per the International Residential Code. See how wide a footing should be for the exact sizing by wall height and soil type.
Dry-lay the first course without mortar to check the layout and spacing, then set it in a full mortar bed and level every block in three directions before it sets. Every course after that runs in a running bond, each block centered over the joint below, for strength and a stable look.
Tool the joints once the mortar is thumbprint hard, drop rebar into the cores called for on the plans, and fill those cores with grout. Cap the top course with solid cap block or a poured bond beam so the hollow cores are not left open to water.
Choosing block width for your wall
The 0.75 blocks per linear foot per course figure holds for any standard CMU width, 4, 6, 8, 10, or 12 inches nominal, since every size shares the same 8 by 16 inch face. Only the wall's thickness, and its load capacity, changes with width. See the full standard concrete block size chart for actual dimensions by width.
An 8 inch block covers most freestanding and foundation walls. Go to 10 or 12 inch block for tall retaining walls or anything carrying heavy soil or structural load, and drop to 4 or 6 inch block for interior partitions that carry no load.
Frequently asked questions
How many blocks do I need to build a wall?
How much do 1000 concrete blocks cost?
Is it cheaper to pour a concrete wall or use blocks?
How many bricks would I need for a 10x10 wall?
How many rooms can 5000 blocks build?
References
- ASTM C90: Loadbearing Concrete Masonry Units
- Concrete masonry unit (Wikipedia)
- NCMA: National Concrete Masonry Association
- NRMCA: Ready Mixed Concrete