How to calculate unit weight of steel bars- With Numerical

For estimation of any structure, you have to calculate volume, weight, length, etc but one question always comes in our mind that, How to calculate unit weight of steel bars? Right?? But don’t worry here we can learn almost every things we required for calculation.

Why do you need to calculate unit weight of steel bars?

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 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. 

What is unit weight of steel bars?

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

Below i have described the simple formula by which you don’t have to remember the 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.

Formula to calculate weight of Steel Bars

unit weight of steel in kg/m3

unit weight of steel formula

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.

Q) Calculate the weight of steel rod of a beam having 8 rod of 6 m length and 16 mm diameter.

How to calculate unit weight of steel bars

          Given, Diameter of rod (D) = 16 mm

                  No. of rod =  8                                                                                  

                                              W = (D2L/162)

                                                    = {(16)2 * 6}/162                                         

                                                     = 9.481 kg

                          But, we have 8 rods.

                        So,   Total weight = 9.481 *8

                                                       = 75.851 kg

Video to Calculate of Weight of Steel rod of Different Diameter

In this way, you can calculate the weight of steel bars simply with the help of diameter and length.

But, keep in mind that the length of the rod must be in meter, and the diameter must be in millimeter.

If they are not, then convert it into a dimension that I have written above.

Steel bar weight Calculator for length in feet With total Cost

I Hope friends, you liked my written article on “How to calculate unit weight of steel bars” and remains helpful.

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"Structural Engineer" with over 5 years of experience in estimation, structural design, and surveying. I am passionate about using my skills to create safe and sustainable structures. I am also a keen writer, and I enjoy sharing my knowledge and experiences with others.