Weight of mild steel square bars can be calculated as

W = 0.00785 s²                                   

where 

W = weight (kg/m)

s = square bar side (mm)

Bar Diameter (mm)	Weight (kg/m)
8	0.50
10	0.79
12.5	1.22
16	2.01
20	3.14
25	4.91
30	7.07
32	8.04
40	12.6
45	15.9
50	19.6
60	28.3
75	44.2
90	63.6
100	78.5