The total weight of steel bars can be determined by calculating the unit weight of each bar. This is calculated after the final estimation of total steel required for a construction project.
In this article, the calculation of the unit weight of steel flat bars and steel rods is explained with examples.
Also Read: Estimation of Steel Reinforcement for slab,beam and column
Unit Weight of Steel Flat Bars
The density of mild steel is 7850kg/m3. A mild steel flat bar is specified by its width and thickness in millimeters. If so, the weight of the steel bar is given by:
Weight of steel bar = Volume of steel Bar x Density of steel
Weight of steel Flat bar = (Length x width x thickness) x 7850
Example 1: Determine the unit weight of MS Flat bar of width 40mm and Thickness of 20mm.
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 .040 x .020) x 7850
= 6.28kg/m
Also Read: Reinforcement Quantity Estimation
Unit Weight of Steel Rods
Here, the density of steel is taken as 7850kg/m3. A mild steel round bars are specified by their diameters in millimeters(mm). If so, the weight of the steel bar is given by:
Weight of steel bar = Volume of steel Bar x Density of steel
Weight of steel rod = (Cross sectional area of steel rod x Length) x 7850kg/m3
= (3.14 x (D2 /4) x L) x 7850kg/m3
= (D2 x 6162.25L)/1000000
= D2 L x 0.006162 = D2 L / 162.28
Weight of Steel Bar = [ D2 L / 162.28] in Kg and Length ‘L’ in m
Weight of Steel Bar = [ D2 L / 533] in Kg and Length ‘L’ in foot
To calculate the unit weight, length “L’ becomes unity.
Example 2: Determine the unit weight of 10mm and 12mm diameter steel bars.
The formula is :
Weight of Steel Bar = [D2 L / 162.28]
Hence, the weight of :
- 10mm dia bar = (10x10x1)/162.28 = 0.616kg
- 12mm dia bar = (12x12x1)/162.28 = 0.8874kg
There is no exact method to calculate the weight of steel. Determination of weight based on the cross-sectional area as explained above does not give accurate results. It is mostly recommended to follow the manufacturer’s unit-weight chart in order to calculate the weight of the steel bars.