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For estimation of any structure, you have to calculate volume, weight, length, etc according to material required for construction. But here you are only going to learn how to calculate the unit weight of steel rod used for constructional work. 

Suppliers provide you total rod by weighing it, but you have to use it at a different section of the structure. At that time you have to calculate the weight of a different piece of steel which is impossible to weight all steel rods individually. 

Also, sometimes we are required to separate the required amount of steel rod for different purposes but at that time there are not the weight measuring tools. You have an only a length measuring device. So, it is very necessary to have knowledge about the calculation of the unit weight of steel rod having a different diameter. 

Unit weight of steel rod is nothing but the weight of steel rod having a one-meter length of the given diameter. i.e by only measuring the length of the rod you can calculate the weight of steel rod of any diameter. 

Steel bars come in different diameter 8mm, 10mm, 12mm, 16mm etc. But, also you can’t remember the unit weight of individual rods having a different diameter. 

Watch Video on Calculation of Weight of Steel rod of Different Diameter

Below i have described the simple formula by which you don’t have to remember diameter, or weight of individual steel rod to calculate its weight. Just measure length and diameter, and calculate its weight using formula i have described below.

The formula to calculate weight is ,

W = (D²L/162)


W = Weight of steel bars.

D = Diameter of steel bars in millimeter (mm).

L = Length of bars in meter (m). 

And remember the unit of calculated weight will be in kilogram (Kg).

Now, let us take an example.

Q) Suppose you are given to calculate the weight of 40-meter rod of 12 mm diameter.

Then, what will you do?

Use above formula,


           D= 12 mm (millimeter)

           L= 40 m (meter)


We have, 

               W = (D²L/162)

       So, W = 12² x 40/162 = 35.5 kg

Weight of 40 m length having 12mm ø bar is 53 kg.

Let’s take another example.

Q) Suppose you are given to calculate the weight of 80 m steel bar having 16 mm diameter (ø).

Very simple do same as above,


           D= 16 mm

           L= 80 m


We have, 

               W = (D²L/162)

     So, W = 16² x 80/162 = 126.41 kg

Weight of 80 m length having 16 mm ø bar is 53 kg. 

If you want to calculate the unit weight of the rod then simply put the length of rod one (1) meter of required diameter in the above formula.

For further better understanding, I have solved another question for you below.

In this way you can calculate the weight of rod simply with the help of diameter and length but keep in mind that the length of the rod must be in meter and diameter must be in millimeter. If they are not, then convert it into a dimension which I have written above.

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