Cement Block Wall Calculator

Last updated: 28 Oct 2025 | Author: Brij | Review By: Irshad

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Easily estimate how many cement blocks you need for your wall using our Cement Block Wall Calculator. Enter wall dimensions, block size, and waste percentage to get instant results with formulas and examples.

Wall Length:

Wall Height:

Block Length:

Block Height:

Mortar Thickness (optional):

Waste Percentage (optional):

Block Wall Calculation Results

Total Wall Area:

sq ft

Block Area:

sq ft

Number of Blocks Required (without waste):

blocks

Total Blocks Required (with waste):

blocks

Mortar Volume:

cu ft

Building a concrete block wall requires accurate estimation of the number of cement blocks, total wall area, and mortar volume. The Cement Block Wall Calculator helps you quickly find out how many blocks you’ll need for your wall project, including waste allowance.

Step by step calculation of Cement Block Wall

Formula to Calculate Wall Area

$\text{Wall Area} = \text{Wall Length} \times \text{Wall Height}$

Formula to Calculate Block Area

$\text{Block Area} = \text{Block Length} \times \text{Block Height}$

Formula to Calculate Number of Blocks Required (without waste)

$\text{Number of Blocks} = \frac{\text{Wall Area}}{\text{Block Area}}$

Formula to Include Waste Percentage

$\text{Total Blocks with Waste} = \text{Number of Blocks} \times (1 + \frac{\text{Waste Percentage}}{100})$

Formula for Mortar Volume (Optional)

$\text{Mortar Volume} = \text{Total Wall Volume} - (\text{Block Volume} \times \text{Number of Blocks})$

Example Calculation

Let’s calculate the number of blocks required for a wall.

Given:

Wall Length = 20 ft
Wall Height = 10 ft
Block Length = 16 in = 1.33 ft
Block Height = 8 in = 0.67 ft
Waste = 5%

Step 1: Calculate Wall Area

$\text{Wall Area} = 20 \times 10 = 200 \, \text{sq ft}$

Step 2: Calculate Block Area

$\text{Block Area} = 1.33 \times 0.67 = 0.89 \, \text{sq ft}$

Step 3: Calculate Number of Blocks (without waste)

$\text{Number of Blocks} = \frac{200}{0.89} = 225$

Step 4: Add Waste

$\text{Total Blocks with Waste} = 225 \times (1 + \frac{5}{100}) = 236.25$

Final Answer:

You’ll need 236 cement blocks (including 5% waste) to build your wall.

Frequently Asked Questions

1. How do I calculate the number of cement blocks for a wall?

Divide the total wall area by the area of one block, then add a waste percentage (usually 5–10%).

2. What is the standard size of a cement block?

A standard concrete block (CMU) is 16 in × 8 in × 8 in (nominal size).

3. How much mortar do I need per block?

On average, mortar accounts for 7–10% of wall volume, depending on joint thickness.

4. How much waste should I include in my block calculation?

Add 5–10% waste to cover breakage, cutting, and misalignment during construction.

5. Can this calculator be used for retaining walls or boundary walls?

Yes, it can be used for any type of wall — just ensure you enter the correct wall dimensions and block size.

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