Dots Per Inch

Calculating your screen's DPI rating is quite easy, first measure your screen's physical width and height (in inches), next divide your screen's native resolution by either your screen's pyshical width or height. For example:

Width: 1680px / 17.1" = ~98 DPI
Height: 1050px / 10.7" = ~98 DPI

After calculating your screen's DPI you can set it through System, Preferences, Font, Details.