Concrete Block Calculator
Calculate the number of concrete blocks needed to build a wall.
Formula
Blocks = ⌈wall length/block length⌉ × ⌈wall height/block height⌉ × 1.05
- Standard CMU block: 8×8×16 in nominal (actual: 7.625×7.625×15.625 in).
- 5% waste factor included.
- Mortar: one 80-lb bag covers approximately 36 standard blocks.
20×8 ft wall, 8×16 blocks
Inputs
- Wall Length: 20 ft
- Wall Height: 8 ft
- Block Height (nominal): 8 in
- Block Length (nominal): 16 in
Rows = ⌈96/8⌉=12; per row = ⌈240/16⌉=15. Total = 12×15×1.05 = 189 blocks.
Frequently asked questions
How much does a standard concrete block weigh?
Standard 8×8×16 CMU weighs about 28–35 lbs depending on type.