# 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**

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.

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