How it works
A nominal 8×8×16 concrete block is a 7-5/8 by 7-5/8 by 15-5/8 in unit. Laid with a 3/8 in mortar joint, each block occupies 8 in by 16 in of wall face, 128 square inches. Since a square foot is 144 square inches, a wall needs 144 ÷ 128 = 1.125 blocks per square foot.
Subtract the area of the openings, multiply by 1.125, and add a waste allowance for breakage and cuts. Mortar, grout, and reinforcing are separate quantities.
Worked example
A 24 ft × 8 ft wall with no openings and 5% waste:
- Net area = 24 ft × 8 ft − 0 ft² = 192 ft²
- Blocks = 192 × 1.125 × 1.05, rounded up = 227
- Courses = 96 in ÷ 8 in = 12; blocks per course = 288 in ÷ 16 in = 18
| Input | Value |
|---|---|
| Wall length | 24 ft |
| Wall height | 8 ft |
| Openings (doors, windows) | 0 ft² |
| Waste allowance | 5 % |
| Result | Value |
|---|---|
| Blocks needed | 227 blocks |
| Net wall area | 192 ft² |
| Courses (rows) high | 12 courses |
| Blocks per course | 18 blocks |
Assumptions and limits
- Standard nominal 8×8×16 block with 3/8 in mortar joints. Other block sizes and half-height units change the count.
- Lintels, corner and half blocks, and bond beams are not counted separately.
- Mortar, grout, and reinforcing steel are not included.
Common questions
How many concrete blocks per square foot?
1.125 for a standard 8×8×16 in block with a 3/8 in mortar joint.
How many courses is an 8 ft wall?
12 courses, since each course is 8 in high including the mortar joint.
How much waste should I allow?
Breakage and cuts vary by job; many builders allow about 5 percent. It is set by you here.
Does this include mortar?
No. Mortar and grout depend on the joint, fill, and mix; use the mortar bag coverage from your supplier.
Sources
- Nominal 8×8×16 concrete masonry unit: 16 in × 8 in module including a 3/8 in joint, 128 in² of wall face, 1.125 blocks per ft².
Updated 2026-09-30