One of my major gripes with a multitude of the websites that I come across in my daily browsing is how difficult they are to read comfortably and without straining one’s eyes. There are many reasons, from bad colour or background usage all the way to more subtle problems such as leading – line height for the uninitiated.

Today, however, I’d like to focus on one aspect of typography in particular. Measure.

Simply put, measure is the length of a line of type.

Short lines are distracting and tiring. They cause the readers’ eyes to flick back to the beginning too often and are a good way to make sure nobody enjoys your content. Long lines break the readers’ pace and rhythm because they have a hard time finding the beginning of the next line. Also a good way to annoy the reader.

So, how long is the perfect line of text? Is there even an answer?

Well, yes, luckily there’s a really easy answer. For optimum readability the best measure would be between 40 and 80 characters per line, including spaces. 65 characters will be ideal for a single column design.

How does one calculate the measure? Simple enough. One can use Robert Bringhurst’s method which takes the size of the type, and multiplies it by 30. So, if one takes a type size of 15, and multiply it by 30, one gets 450 pixels, or about 65 characters per line, give or take.

Here is some example code:

p {
  font-size: 15px;
  max-width: 450px;
}

This also works for em’s.