In previous research on Golden Ratio Typography author focused primarily on the core geometric properties of text—font size, line height, and line width.
But there’s another facet of text that nearly all of the existing research on typography deals with: It’s called characters per line (CPL).
If you’ve ever read a study on typography, you’ve no doubt encountered CPL. Many of these studies recommend “optimal” CPL ranges that include anything from 55 to 100 CPL.
With an “optimal” range that large, the CPL you use on your site ultimately comes down to personal preference. This raises one huge question:
How can you tune your typography to an exact (or, at least approximate) CPL?
Read the rest of article here How to Tune Typography Based on Characters Per Line