I'm writing a thesis, and of course my university has some requirements regarding the typography, specifying in particular the measure (36 pc), the minimum font size (10 pt), and an acceptable range for the leading (1.5 to double spacing).

What is known in general about readability as a function of these parameters and the text font?

I am aware of research showing that lines ranging between 60 and 70 characters optimize ease of reading of single-column text, with longer lines making it harder to pick up the next line. But I don't know if that research only accounts for normal leading (aka single spacing). Increasing the leading will presumably make it easier to pick up the next line after reading a long line?

Because of the university requirements, any reasonable font I choose will produce more than 70 characters per line. So how much should the leading be increased to compensate?

2 Answers 2


See Robert Bringhurst, "The Elements of Typographic Style" version 3.2, section 2.1.2 "Choose a comfortable measure." This book is considered "the bible" of typography. In particular, he says:

... even with generous leading, a line that averages more than 75 or 80 characters is likely to be too long for continuous reading.

This section tells you how to establish a measure (or, conversely, how to establish a point size based on a required measure).

I would bet that there's a copy in your university library. You don't need all of it, but that section will give you what you need.

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    Thank you for the precise reference! I'll look it up at the library tomorrow. Jun 23, 2011 at 2:29
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    Another excellent source of good information for your purposes is the website typographyforlawyers.com, by a typographer-turned-lawyer who finally couldn't stand the typographic trash his colleagues created. The information is accurate, readable, witty and (of course) well typeset. Jun 23, 2011 at 3:36
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    you are a bottomless well of useful information. Seriously, can we make a badge for that? :) Jun 23, 2011 at 12:10
  • Shucks... I like useful bits, so when I see one, my tongue whips out, chameleon-like, and nabs it. Slurp, crunch, crunch. Yummy. After that, it seems a shame not to pass it along. (I'm probably better with mindless trivia, though. Promise not to tell?) Jun 23, 2011 at 17:28
  • Brinkhurst is missing from my university library, so I'll have to wait to explore it. I've seen it recommended before, so I'm definitely looking forward to it. Meanwhile, I'll plan to use a 12pt font that will give me not too much more than 80 characters. I'm still interested in hearing about more empirical research, though a judgment from a renowned expert is worth a lot. Jun 24, 2011 at 1:01

The leading required in school papers is way larger than what people would normally use for a regular text but it allows for more space in-between lines for the teacher to write comments. The best amount of leading for a text really depends on the way your font is drawn (proportions of x-height vs. ascenders and descenders).

Example of different x-heights for the same type size: http://papress.com/thinkingwithtype/letter/letter_images/fat.gif

Personally, I wouldn't mess too much with the guidelines that are required. I was sometimes frustrated as a graphic designer with these requirements but it makes for visual uniformity.

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