For knowing the unit weight of rod per metre length,Let me show you the simple derivation of formula mostly used i.e. D^2/162.2

Its follows as :

Weight of steel bar per meter = Area of the steel x Density of steel x Bar length

= (3.14 x D^2/4)  x  7850 kg/  x 1m

= (D^2 x 6162.25)/(1000 x 1000)

D^2 x (0.006162)

D^2 x 1/(0.006162)^-1

D^2/162.28

For easy calculation in problem solving or calculations we use this formula:

Unit weight of Steel Bar (in Kgs) = D^2/162

Where, D is the Diameter of the Steel Bar in mm.

Remember:

To calculate the unit weight, length “L’ becomes unity.

Weight of Steel Bar  = [ D^2 L / 162.28] in Kg and Length ‘L’ in m

Weight of Steel Bar = D^2 L / 533] in Kg and Length ‘L’ in foot

Here, the density of steel is taken as 7850kg/m3. A mild steel round bars are specified by their diameters in millimeters(mm).

For MS Flat Bar

Weight of steel Flat bar = (Length x width x thickness) x 7850

For example:

MS Flat bar of width = 50mm

Thickness = 30mm.

As we know,

Weight of steel bar = Volume of steel Bar x Density of steel

Weight of steel bar = (Length x width x thickness) x 7850

Unit Weight of steel bar = (1 x .050 x .030) x 7850

= 11.775 kg/m

Note:

If you are calculating the weight of circular steel bar then calculate its volume by using this formula (πD^2/4) and then just multiply by the density of steel which is 7850 kg/

For circular Steel Rods

Formula for Unit weight of steel = D^2/162  kg/m

For example:

If we want to calculate the unit weight of 10mm steel rod of 1-metre height,

Weight of steel = 10^2/162

= 0.617 kg/m  x  1m

= 0.617 kg

So, 1- metre of 10 mm steel weighs around 0.617 kg.

At site,The steel is usually brought  in the big troller and the rod length is about 12 metres.

So, if you want to calculate for 12 metre rod,then

Unit weight of steel for 10 mm steel rod is 0.617 kg

For 12 m=12 x0.617=7.40 kg

So, 12 m long rod of  10mm dia weighs around 7.40 kg

Hence, the weight of :

8mm dia bar = (8x8x1)/162 = 0.395 kg

10mm dia bar = (10x10x1)/162= 0.617 kg

12mm dia bar = (12x12x1)/162= 0.89 kg

16mm dia bar = (16x16x1)/162= 1.58 kg

20mm dia bar = (20x20x1)/162= 2.47 kg

25mm dia bar = (25x25x1)/162= 3.86 kg

32mm dia bar = (32x32x1)/162= 6.32 kg

The table below shows the unit weight of different diameter bars in kg/m

The weight of the steel bar can be calculated in two ways: by Density of steel or by Formula.

Always consider the manufacturer’s unit weight chart in order to calculate the weight of the steel bars. Calculating weights with respect to their cross sectional area does not give accurate results. This is the simple and easiest way to calculate the weight of steel without any interpolations. The total weight of the steel bar can be determined by calculating the unit weight of each bar. It is calculated after the final estimate of the total steel required for a construction project.

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