Concrete Block Calculator
CMU blocks and mortar bags for a wall.
Reviewed by the Calculation Machine team · How we check our maths
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.
The formula
blocks = ceil(wall area / block face area x (1+waste%))
Worked example
Worked example
Using the values the calculator loads with.
Inputs
- Wall length30 ft
- Wall height8 ft
- Block width16 in
- Block height8 in
- Waste allowance5 %
Result
- Blocks needed284
- Wall area240 sq ft
- Mortar bags (80 lb, ~33 blocks/bag)9
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.
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 the Calculation Machine team · How we build and test calculators
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