Study: The Effects of Line Length on Reading Online News (2008)

Ironically, the html version of the text has 305 character long lines on a 1080p monitor =P.

The results of the study are a bit counter-intuitive for me. I prefer to read and write software with <80 cpl, and find it difficult to read programs with longer lines. Maybe the difference between reading articles and software is to great to expect the same kind of outcome. In any case I don't think 95 cpl is an extreme enough line length to be really interesting. It would have been nice if they had run the study with more testing points at longer and longer lines until they found a point where reading speed dropped or comprehension suffered (if there is such a point, maybe not?)

> I prefer to read and write software with Maybe the characters per line is not the relevant data point. The fact that there are so many studies that give wildly varying results using this measure seems to be a strong indicator that this is the case.

They chose specific font metrics, and used a single monitor at a single distance in a single context, so they have no way of knowing whether it was the physical width, the pixels per degree, or some other factor that they were actually measuring.

Think of it this way: if they had doubled the text size, that would undoubtedly have resulted in far wider line lengths in physical terms, yet the characters per line would have remained the same. If they rigged the conditions so the physical width and characters per line were fixed in lockstep, were they measuring responses to the number of characters per line, or were they really measuring responses to physical width? There's no way of knowing with this study.

Any study like this that could usefully be applied to the web needs to take into account varying font sizes and all the other things that make the web different from print. Fixed font sizes in pt is not how the web operates.

The result was that the highest reading speed was at the longest line length they tried, 95 characters. They should have tried longer line lengths until the reading speed dropped again. All they can say now is that the maximum speed was achieved at a line length of 95 or greater.