The exact diameter needed for your document varies based upon the thickness of the inner sheets of paper as well as the covers. Below is a chart that provides recommendations based on both the number of pages (using regular 20# bond) and the thickness of the stack being bound.
| Pages | Thickness | Wire Size |
|---|---|---|
| 5-20 | 1/8" | 3/16" |
| 20-30 | 3/16" | 1/4" |
| 30-50 | 1/4" | 5/16" |
| 50-60 | 5/16" | 3/8" |
| 60-80 | 3/8" | 7/16" |
| 80-100 | 7/16" | 1/2" |
| 100-120 | 1/2" | 9/16" |
| 110-140 | 9/16" | 5/8" |
| 140-160 | 5/8" | 3/4" |
| 160-190 | 3/4" | 7/8" |
| 190-220 | 7/8" | 1" |
| 220-240 | 1" | 1-1/8" |
| 240-260 | 1-1/8" | 1-1/4" |
Please note: Wire sizes listed in red are 3:1 pitch; wire sizes listed in black are 2:1 pitch.