How to calculate weight of mild steel bar?

Weight	=	Volume x density
Since its cylindical shape
Volume of bar	=	pi()*h*(d²)/4	mm³
	where	h is height of cylinder bar
		d is diameter in mm
Weight density of steel	=	7850	kg/m³
Here we considering for 1m length, so h = 1m
Volume of bar	=	pi()*h*(d²)*(10⁻⁶)/4	m³
	=	pi()/4*h*(d²)*(10⁻⁶)
Here we have coverted dia from mm to m
Volume of bar	=	(7.85*(10⁻⁷))*(d²)	m³
Weight of bar	=	Weight density x Volume
or unit weight of steel	=	7850*(7.85*(10⁻⁷))*(d²)
	=	0.00616225	*d²
or can be written as	=	d²/	162
		where d is diameter of bar in mm
Example
25mm bar weight per meter =		25*25/162
	=	3.858024691	kg
Weight of steel	=	(d²/162)*length