Well I am going to answer it according to the size of brick block used in our part of world more closely in Pakistan.By the way its cannot be done by the person who even don't know mathematics and who is not expert in civil engineering.It'S a structural engineer's job.Not everybodies headache.Let's back to the point. Well it can be calculated by many ways.There are 1350 No. Of bricks used for a 100 square feet wall.In this cae the size of the brick used is 9"x4.5"x3"i.e. 9" is the lenght,4.5"is the width and 3" is the depth of the brick.According to this you can find out the No. Of bricks in a wall.The other method used is more mechanical and it cannot be understood by ordinary people,but for the sake of your concern I m going to write it in short. Well first of all take the central lenght of all the walls used in the room plan.Calculate the sum of it.Now multiply it by the height of the room and thickness of the brick.It's the total quantity in cubic feet.now multiply it by 14 to calculate the total no. Of bricks used in a room.It's the number of bricks used in superstructure I.E. Structure above finish floor level.For the foundation or substructure the rule is the same but sum of central line has to be multiplied by the width of the foundation footing(1st,2nd,3rd,4th,5th,6th exclusively) and height of each footing.then get the quantity in cubic feet.then sum up all the footing values and multiply it by 14 to find the no. Of bricks in sub structure.In the last step add the amount of number of bricks in sub structure and in super structure. Here in this way you will get the total number of bricks used in the constuction of the room.
This is normally the job of a quantity surveyor who should enjoy maths.
You would work out the surface area of the wall in question and then knowing the surface area of a brick, would then divide the area of the wall by that ,and get a figure for how many bricks are in the wall.
To calculate the surface area of a layer of single bricks, the wall, or the brick, for that matter.
You would take the width of the wall by the height of the wall, and mutiply them by each other.
Then with the result, you would decide how thick you want the wall, normally it is two bricks thick these days, and so you could just double the result that you got for the wall.
This would give you the quantity of bricks, if you then divide the surface area of the wall, by the area of one brick. you will have your quantity.