Concrete Block Calculator
Enter your wall dimensions to estimate the number of concrete blocks (CMU) and bags of mortar needed, based on standard 16×8 inch block coverage.
Results
- Blocks needed
- 199 blocks
- Mortar bags (approx.)
- 7 bags
- Wall area
- 160 sq ft
Estimates only. Round up and buy a little extra to account for waste, spills, and breakage.
Enter your wall dimensions to estimate the number of concrete blocks (CMU) and bags of mortar needed, based on standard 16×8 inch block coverage.
How to use the concrete block calculator
- Enter the wall length in ft.
- Enter the wall height in ft.
- Enter the openings to subtract in sq ft.
- Enter the waste factor in %.
- Optionally add a price to estimate the total project cost.
- Read your quantities instantly — no sign-up, and you can print the estimate to take to the supplier.
Worked example
Inputs
- Wall length
- 20 ft
- Wall height
- 8 ft
- Openings to subtract
- 0 sq ft
- Waste factor
- 10 %
Results
- Blocks needed
- 199 blocks
- Mortar bags (approx.)
- 7 bags
- Wall area
- 160 sq ft
Using the example values above, the concrete block calculator returns 199 blocks (blocks needed). Change any field to match your own project and the numbers update instantly.
How much extra should I order?
Always order a little extra. A 5% waste factor suits simple, square projects; 10% is right for most jobs; bump it to 15–20% for irregular shapes, diagonal patterns, or uneven ground. Running short almost always costs more than the leftover material.
Formula
Blocks = wall area × 1.125 (per sq ft for 16×8 block), × (1 + waste%). Mortar ≈ 1 bag per 30 blocks.
Frequently asked questions
- How many concrete blocks per square foot?
- A standard 16×8 inch CMU covers about 0.89 sq ft, so you need roughly 1.125 blocks per square foot of wall.
- How much mortar for a block wall?
- Plan about one 80 lb bag of mortar mix for every 30–35 standard blocks laid.
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