Concrete Masonry Block Calculator
Calculate the number of CMU concrete blocks needed for any wall. Includes mortar and grout estimates.
🧱 Construction📐 Blocks = Wall Area / Block Face Area
Wall length (feet)
Wall height (feet)
Block length (inches)
Block height (inches)
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Concrete Masonry Block Calculator | Blocks = Wall Area / Block Face Area | blocks |
Step-by-Step Examples
Example 1
Standard Block Wall
30 ft × 8 ft, 16×8 inch blocks.
- Area: 240 sq ft | 8×16 block = 0.889 sq ft
- Blocks: ceil(270) + 5% = 283 blocks
✓ 283 blocks
Example 2
Short Retaining Wall
20 ft × 4 ft, 16×8 blocks.
- Area: 80 sq ft | ~100 blocks total
✓ ~100 blocks
Example 3
Garage Block Wall
50 ft × 10 ft, 16×8 blocks.
- Area: 500 sq ft | ~590 blocks
✓ ~590 blocks
Real-World Applications
Masonry Contractors
Calculate block quantities for any CMU wall.
Estimators
Quick masonry material takeoff for bids.
Homeowners
Estimate DIY block wall materials.
Builders
Plan masonry wall material orders.
Common Mistakes to Avoid
⚠️
Not adding waste factor
Always add 5-10% for cuts, breakage, and waste. For complex walls with lots of cuts, use 10%.
⚠️
Wrong block dimensions
Standard CMU is 8×8×16 nominal (7.625×7.625×15.625 actual with mortar joints).
Frequently Asked Questions
Standard CMU block sizes? ▾
Most common: 8×8×16. Also: 4×8×16, 6×8×16, 12×8×16. Face area of 8×8×16 = 0.889 sq ft → 1.125 blocks/sq ft.
How much mortar per block? ▾
About 1 bag (90 lb) of mortar per 40-50 standard CMU blocks. 1 bag yields approximately 0.5 cubic feet of mortar.
CMU vs brick? ▾
CMU is larger and faster to lay. Brick is smaller and more decorative. CMU is structural; brick is often veneer over structural backing.