Weight of mild steel round bars can be calculated as

W = 0.0062 d2                            (1) 

where 

W = weight (kg/m)

d = round diameter (mm)

Bar Diameter
(mm)
Weight
(kg/m)
6 0.22
8 0.39
10 0.62
12 0.89
16 1.58
20 2.47
25 3.85
32 6.31
40 9.86
45 12.5
50 15.4
60 22.2
65 26.0
75 34.7
90 49.9
100 61.6