Line length and page margins

Line length is the average number of characters per line in a text block. The page margins control the overall size of the text block, and thus have the greatest effect on line length (of course, font choice and font size also affect line length, though more finely). As the page margins increase, the line length decreases.

Shorter lines are more comfortable to read than longer lines. As line length increases, your eye has to travel farther from the end of one line to the beginning of the next, making it harder to keep your place vertically. (That’s why newspaper columns are so narrow—newspaper columns are tall and thus it’s important to make vertical tracking as easy as possible.)

While there is no blackletter rule, aim for a line length of 50 to 90 characters (including spaces). You can check the line length of a sample text using the word count function of your word processor: select a series of lines and use word count to show the number of characters in each.

You can also use the easy “alphabet test” to set line length: type every lowercase letter from a to z. You should be able to fit 2 to 3 alphabets on your line, like so—

abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmno

Shorter line lengths will make a big difference in the legibility and professionalism of your document. Most nonprofessional typographers, lawyers included, make their lines too long. This is probably because most word processors set the page margins at 1 inch by default. While that was fine in ye olde days when we used monospaced fonts, it’s too small for most proportional text fonts.

Generally, page margins of 1.5 to 2 inches will give you a comfortable line length if your text is set at 12 point. But focus on getting the number of characters per line into the right range. The smaller your font size, the larger your margins will need to be, and vice versa.