### 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**

Where,

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

Where,

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

Therefore,

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.

## Comments ( 8 )

How can find the volume of cement of 50kg without using its density ?

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I thank you so much. You are really helping me to improve

This information is really helpful,thanks a lot…

Nice&helpful for all civil engineers.thanks

Thanks.Good information for civil engineers.