How to findout weight of steel bar

Steel bar of the weight extract in the formula is the useful.

Formula :- weight = Diameter x Diameter ÷ 162

Diameter is the meaning of the mm of steel bar.

For example :- 8mm steel bar
              w = Diameter x Diameter ÷ 162

                w = 8 x 8 ÷ 162 = 0.39 kg / m

Steel bar is in the one meter of weight 0.39 kg/m.
              w = 0.39 x 12 = 4.68 kg
Steel bar is twelve meter weight of4.68 kg.