The size of text on your WordPress website depends on the theme which is installed for your site. Different themes have different default fonts. For most the default font size is 12 points, but different fonts look different, even at a given point size. If you find the text on your site’s pages is too small or too large, you can follow the instructions below.You could also choose to install a different theme. This is not difficult, and does not change your site’s content at all, just colors and text styles. Themes frequently handle the header differently, however. For instance, the vertical banner dimension varies greatly among themes. So, although changing your theme is easy with respect to the content of posts, it involves some re-working of the header.
That said, below is the easiest way to make the text on any web page either larger or smaller:
The viewing size of text depends upon the resolution of the screen. High resolution screens show the text smaller than lower resolution ones. To increase the size of text on any web page, hold down the Ctrl key and then press the “+” key (on Windows); or on Mac, hold down the Command key and then press the “+” key. To reduce text size, the procedure is the same, but press the “-” (minus) key, instead of the “+” key.
— TCDavis
