ConstructionInstant Tool
Concrete Block Calculator
Calculate CMU concrete blocks, mortar bags, and wall courses
Concrete Block Estimator
Calculate CMU blocks, mortar bags, courses, and wall surface area
How Concrete Block Calculator Works
Blocks = Wall Length in Feet × Wall Height in Feet / 0.889 × 1 + Waste FactorCalculates concrete masonry units required by dividing total wall surface area in square feet by the standard nominal face area of an 8x16 inch block 0.889 square feet including 3/8-inch mortar joint.
Variable Breakdown
L
Wall LengthTotal horizontal length of the masonry wall in feet
H
Wall HeightTotal vertical height of the wall in feet
A
Block Face AreaNominal surface area per block standard 0.889 square feet
Waste
Waste FactorAllowance for corner cuts, half blocks, and breakage
Example Calculation
30 by 8 Foot Retaining Wall with 10% Waste
A contractor builds a 30 foot long by 8 foot high retaining wall using standard 8x8x16 CMU blocks with a 10 percent cutting allowance.
- Total wall area equals 30 multiplied by 8 which equals 240 square feet
- Net blocks required equals 240 divided by 0.889 which equals 270 blocks
- Adding 10 percent waste equals 297 total blocks to order
- Wall courses equals 8 feet multiplied by 12 divided by 8 inches which equals 12 courses high
- Mortar required equals 297 divided by 100 multiplied by 3 which equals 9 bags of 80 lb mortar
Result:297 CMU Blocks and 9 Mortar Bags
Concrete Block Nominal Dimensions and Coverage
| Block Size | Actual Dimensions | Face Area Sq Ft | Blocks per 100 Sq Ft |
|---|---|---|---|
| 8x8x16 CMU | 7.625 x 7.625 x 15.625 in | 0.889 sq ft | 112.5 blocks |
| 4x8x16 CMU | 3.625 x 7.625 x 15.625 in | 0.889 sq ft | 112.5 blocks |
| 6x8x16 CMU | 5.625 x 7.625 x 15.625 in | 0.889 sq ft | 112.5 blocks |
| 12x8x16 CMU | 11.625 x 7.625 x 15.625 in | 0.889 sq ft | 112.5 blocks |
| 8x4x16 Half Height | 7.625 x 3.625 x 15.625 in | 0.444 sq ft | 225.0 blocks |
Frequently Asked Questions
How many concrete blocks are in a square foot?
A standard nominal 8x8x16 inch concrete block covers 0.889 square feet. Therefore, you need approximately 1.125 blocks per square foot of wall area.
How much mortar do I need per 100 concrete blocks?
You need approximately 3 bags of 80-pound Type S or Type M masonry mortar per 100 standard CMU blocks.
What is the actual size of an 8x8x16 concrete block?
The actual dimensions are 7-5/8 inches high, 7-5/8 inches wide, and 15-5/8 inches long. When laid with a standard 3/8-inch mortar joint, the block occupies nominal 8x8x16 inches.
How many concrete blocks are on a pallet?
A standard manufacturer pallet holds between 108 and 120 concrete blocks of nominal 8x8x16 dimensions, weighing approximately 3600 to 4000 pounds.
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