Here is a table I found on this subject:
wire diameter (in inches): crimp tube size:
.010- 013 1
.015-.021 2
.024 2,3
.026 3,4
.030 4
.036 4
I am not sure if these sizes are all right, because I have not worked with so many sizes of wire. I also know that crimp bead sizes are slightly different. Anyway, I hope this helps!!!