concrete blocks are available in many sizes and shapes, and have a wide range of physical properties. They can be hollow or full, made from light cement or made of very dense aggregates.
Calculating the amount of blocks needed for a building is a simple process that requires no prior knowledge of building or architecture.
There are several methods for calculating the number of blocks in a wall. I will explain two simple methods for finding the total number 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.