Concrete Block Calculator
CMU blocks and mortar bags for a wall.
Enter your values
ⓘ Live results
Results
- Blocks needed
- 284
- Wall area
- 240 sq ft
- Mortar bags (80 lb, ~33 blocks/bag)
- 9
Quick answer
Block count is wall area divided by the face area of one block, plus waste, and mortar scales with block count.
blocks = ceil(wall area / block face area x (1+waste%))
How to use the Concrete Block Calculator
- 1Measure the wall length and height.
- 2Enter the block face dimensions, standard CMU is 16x8 in.
- 3Add 5-10% waste and figure roughly one 80 lb mortar bag per 33 blocks.
Worked example
Using the values the calculator loads with:
Inputs
- Wall length30 ft
- Wall height8 ft
- Block width16 in
- Block height8 in
- Waste allowance5 %
Results
- Blocks needed284
- Wall area240 sq ft
- Mortar bags (80 lb, ~33 blocks/bag)9
Frequently asked questions
How many blocks per bag of mortar?
About 33 standard 8x16 blocks per 80 lb bag of mortar, less for thicker joints.
Do I need rebar and grout?
Load-bearing block walls usually need vertical rebar and grouted cores per your local code.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.