**1- Surface area method**

**2- Volume method**

**1- Surface area method**

Required data

1- Surface area of the wall.

2- Surface area of a standard concrete block.

3- Surface area of openings in the wall.

**Step 1:**

Determine The Length & Height Of The Wall:

Let, the Length of the wall = 10 feet.

The height of the wall = 10 feet.

**Step 2:**

Calculate The Surface Area Of The Wall:

We know, Surface Area = Length x Height

∴ Surface area of the wall = 10 x 10 = 100 sq. feet.

**Step 3:**

Calculate The Surface Area Of Openings:

If the wall has any openings such as door, windows etc, calculate the surface area of openings.

Let the wall has a window of 3′ x 3′

∴ Surface area of the window = 3 x 3 =9 sq. ft

**Step 4:**

Substract The Surface Area Of Openings From Surface Area Of Walls:

∴ Final Surface Area of wall = 100 – 9 = 91 sq.ft.

**STEP 5:**

Calculate The Surface Area Of A Concrete Block With Mortar Allowance:

Let the block is 16″ x 8″ x 8″ and mortar allowance is 1″

∴ Surface Area of one block with mortar = length * height = (16+1) x (8+1)= 153 inch²

= 153/12×12 = 1.0625 sq.ft

**Step 6 :**

Divide The Total Surface Area Of The Wall By Surface Area Of One Block:

∴ Number of blocks = Surface Area of wall/Surface Area of a block = 91/1.0625 = 86

Consider 5% wastage of concrete blocks.

So the total numbers of blocks required = 86 + (86 x 5/100) = 86 + 4 = 90.

**2- Volume method**

**Required data**

1- Volume of the wall.

2- Volume of a standard concrete block.

3- Volume of openings in the wall.

**Step 1:**

Determine The Width, Height, And Thickness Of The Wall:

Let, the width of the wall = 10 feet.

The height of the wall = 10 feet.

The thickness of the wall = 8″ = 0.67 feet. [ Thickness of wall will be same as the thickness of one concrete block]

**Step 2:**

Calculate The Volume Of The Wall:

We know, Volume = Width x Height x Thickness

∴ Volume of the wall = 10 x 10 x 0.67 = 67 cubic feet.

**Step 3:**

Calculate The Volume Of Openings:

If the wall has any openings such as door, windows etc, calculate the volume of openings

Let the wall has a window of 3′ x 3′ x 0.67′ [ Thickness of the window will be same as the thickness of the wall]

∴ Volume of the window = 3 x 3 x 0.67 =6 cu. ft

**Step 4:**

Substract The Volume Of Openings From Volume Of Walls:

∴ Final volume of wall = 67 – 6 = 61 cu.ft.

**Step 5:**

Calculate The Volume Of A Concrete Block With Mortar Allowance:

Let the block is 16″ x 8″ x 8″ and mortar allowance is 1″

∴ Volume of one block with mortar = (16+1) x (8+1) x 8 = 1224 inch3 [The mortal will be given on the upper side and one side of every concrete block]

= 1224/12x12x12 = 0.70 cu.ft

**Step 6:**

Divide The Total Volume Of The Wall By Volume Of One Block:

∴ Number of blocks = Volume of wall/Volume of a block = 61/0.70 = 86

Consider 5% wastage of concrete blocks.

So the total numbers of blocks required = 86 + (86 x 5/100) = 86 + 4 = 90.

**Note:**

If the wall does not have any opening **skip step 4,** and just divide the surface area of wall by the surface area of one block.