 Cement or concrete blocks are available in several sizes and many shapes, and have a wide range of physical properties. They may be hollow or solid, made from lightweight cement or be formed from very dense aggregate. Specialist cement blocks have additional benefits such as high thermal and sound insulation properties.

Calculating the quantity of blocks needed for a building is a straightforward process that does not require any previous building or architectural skills. There are several methods for calculating number of blocks in a wall. In this article, I will explain two simple methods to find out total no. of blocks for a wall.

###### 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.