Why is it important to calculate the weight?
✓ Steel is Sold by Weight, not by Pieces
✓ Quantity Surveyor uses Bill of Quantities (BOQ) and it is based on mass not pieces
✓ Structural Design Calculations are based on loads/weight
How to Calculate Steel Bars’ Weight?
Steel bars can be calculated using two methods:
- by using the density of the steel
- by converting the diameter to the weight.
Standard Formula using Steel’s Density
Weight = Volume × Density
For a round steel bar:
Multiplying the volume and the density of the steel, we get
Where:
- W = Weight in kg
- D = Diameter in meters
- L = Length in meters
For Example: A 20 mm diameter bar and 10 m length:
Shortcut Formula (used on site)
Most Engineers use this formula as it is more convenient and easy to calculate:
The value of D is in millimeters.
This gives you the weight in kg for 1 meter of steel bar.
For Example: A 20 mm diameter bar:
So if we are estimating 10 meters of 20 mm rebar:
Conclusion
If we compare the two, there’s only a slight difference in decimal; therefore, it is up to you which one you prefer to use in your solution.
