---
name: Measure
slug: measure
category: typography
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: The width of a column of text, judged in characters per line, with
  roughly 45 to 75 treated as the comfortable range for reading.
aliases:
  - name: line length
  - name: column width
  - name: characters per line
  - name: CPL
tags:
  - editorial
  - perception
  - spacing
relations:
  contrastWith:
    - leading
    - text-columns
    - ch-unit
  variantOf: []
  partOf: []
  seeAlso:
    - reader-mode
    - text-balancing
implementations: []
sources:
  - title: Choose a comfortable measure (Elements of Typographic Style Applied to
      the Web)
    url: http://webtypography.net/2.1.2
  - title: "Readability: The Optimal Line Length (Baymard)"
    url: https://baymard.com/blog/line-length-readability
demo: inline
exhibit: false
useWhen: deciding how wide a paragraph is allowed to get
---

The word is letterpress. A compositor set the composing stick to a width, in
picas, and that width was the measure; every line in the job was built to it. What
carried over to the screen is the habit of stating it in characters rather than in
picas or pixels, because the constraint is about the eye and not about the paper.
At the end of every line the eye has to sweep back and drop one line, and the
longer the sweep, the more often it lands on the line it just read.

The numbers everyone quotes come from Bringhurst: anything from 45 to 75
characters is satisfactory for a single-column page, and 66 characters, counting
letters and spaces, is the figure he calls ideal. Treat that as a well-chosen
convention rather than a finding. The research underneath is messier and mostly
says two things at once: readers often move through longer lines slightly faster,
and they reliably prefer and report better comprehension with shorter ones. When
speed and preference disagree, interface text should follow preference, since
nobody is being timed.

In CSS the unit that matches the concept is `ch`, the advance width of the zero
glyph, so `max-width: 66ch` is the direct translation. It runs a little wide in
practice, because in most faces a zero is wider than an average lowercase letter
and much wider than a space, which means a 66ch column holds closer to 70 or 75
characters. Setting somewhere around 60ch usually lands on Bringhurst's 66 in
real text. The newer `lh` and `rlh` units make the companion adjustment easy to
state, since a long measure needs more [leading](/leading) to keep the return
sweep from missing its target, and a short one needs less.

Measure is the setting a full-width layout forgets. A paragraph in a `div` with no
constraint inherits the viewport, which on a wide monitor is 200 characters and
unreadable, and the fix is a maximum on the text column rather than a maximum on
the page. The other failure is a measure so narrow that every line breaks after
four or five words: the rag turns violent, hyphenation starts working overtime,
and the paragraph reads as a list.