The Formula D²L/162 For Calculating Weight Of steel Bars Fully Derived

The Formula D²L/162 Fully Derived:

To calculate the weight of steel bars you must use the formula D²L/162, but do you know where the formula D²L/162 came from? Okay, no problem if you don’t know. In this article, I will share how to derive the formula D²L/162. So let’s start from the beginning.

The formula is D²L/162


D = Diameter of steel bar in millimeter
L = Length of steel bars in meter

Calculation Of The Formula D²L/162:

We know that,

Weight= Cross sectional area x Length  x Density

For steel bar, this also remains same.

The weight of steel bars= Cross sectional area of steel bar x Length of steel bar x Density of steel bar.

That means,

W = A x L x ρ


W = Weight of steel bars
A = Area = πD²/4
π (pi) = 3.14
D = Diameter of steel bar in millimeter
L = Length of steel bar in meter
ρ (Rho) = Density of steel bar = 7850 kg/m³


W = 3.14 x D²/4  x L x 7850

But there is two conflicting unit in the formula. Which is millimeter for D and meter for ρ (Rho).

So we need to convert either D or ρ to the same unit.

Let’s change the unit of D from millimeter to meter.

1 millimeter = 0.001 meter

Let’s put this into the formula,

W= 3.14 x {(D² x 0.001 x 0.001)/4} x L x 7850

= D²L/162

Hope you all understood this calculation. Using this formula we can easily calculate the weight of steel bars.

Also Read – 10 + Thumb Rules For Concrete Mix Design
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