What size type?
This is a question I am often asked.
However it’s difficult to answer with absolute certainty because some typefaces look larger than others at the same size.
The typeface Perpetua, created by Eric Gill in 1925, is a beautiful typeface. It was designed with a small x-height—literally the height of the lowercase letter x. It has long, ascenders and descenders which are the lines that extend above and below the x-height.
The typeface Helvetica, designed by Max Miedinger in 1957, is also a beautiful typeface. It has a taller x-height than Perpetua, and shorter ascenders and descenders.
If I answer the question this way, “Use 11 point type for setting text,” I would get two different looking results depending on whether I use Perpetua or Helvetica.
Here’s what I mean. Although difficult to believe, both typefaces are the same size, but Helvetica appears the larger of the two typefaces because of the way it was designed.
[You may want to enlarge the image below by clicking it.]
Below are the same typefaces which I have visually balanced to appear to be the same size.
Perpetua is still 11 points in size but to make Helvetica appear the same size, I reduced it to 8.5 points, almost 25% smaller in absolute typesize than Perpetua.
And so the only useful answer to this question is, “It depends on the typeface. But as a starting point use type that is between 9 and 12 points in size, and then print a sample of the page to check how easy the type is to read.”