line length45–90 characters or 2–3 alphabets

Line length is the dis­tance be­tween the left and right edges of a text block. Overly long lines are a very com­mon prob­lem. But they’re easy to cor­rect. Shorter lines will make a big dif­fer­ence in the leg­i­bil­ity and pro­fes­sion­al­ism of your layout.

The most use­ful way to mea­sure line length is by av­er­age char­ac­ters per line. Mea­sur­ing in inches or cen­time­ters is less use­ful be­cause the point size of the font af­fects the num­ber of char­ac­ters per inch. Av­er­age char­ac­ters per line works in­de­pen­dently of point size.

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 track your progress vertically.

Aim for an av­er­age line length of 45–90 char­ac­ters, in­clud­ing spaces. You can check line length us­ing word count.

How to use word count

Word ReviewProofing panel → Word Count (icon looks likeABC” above123”)

OS X Word ToolsWord Count

Pages ViewShow Word Count. When the word-count dis­play ap­pears, click its right edge and switch it to Characters With Spaces.

Al­ter­na­tively, use the al­pha­bet test to set line length. You should be able to fit be­tween two and three al­pha­bets on your line, like so:

= 2.31 alphabets

This is es­pe­cially use­ful when you don’t have easy ac­cess to word counts, for in­stance in a web layout.

by the way
  • If you plan to use in­dent­ing to dis­tin­guish sec­tions or hi­er­ar­chies within your doc­u­ment, take this into ac­count when set­ting up the ini­tial line length. You want to start with long enough lines so that the in­dented parts also fall within the tar­get range. Us­ing fewer lev­els of in­den­ta­tion, and smaller in­dents, will help.

  • The ma­jor flaw in many re­spon­sive web lay­outs? In­suf­fi­cient at­ten­tion to line length. Nav­i­ga­tion and im­ages are care­fully en­gi­neered to scale up and down, but the body text is al­lowed to re­flow hither and yon. Not good. If you need the body text to fit a broad range of widths, then use ad­just­ments to point size and page mar­gins to keep the line length in the right range. Don’t just rely on reflow.