Your biker jacket thickness is an important indication as to how much protection you are actually wearing.  Below is a chart to use when shopping online for relative comparison.   

Ounces
Fractional Inches
Millimeters
1
1/64
0.41
2
1/32
0.78
3
3/64
1.19
4
1/16
1.60
5
5/64
1.98
6
3/32
2.39
7
7/64
2.78
8
1/8
3.18
9
9/64
3.58
10
5/32
3.96

For more information on this topic we will refer you the motorcycle leather experts at Chilhowee.net