Content & Messaging
Line Length (Measure)
Lines of body text that are too wide force the eye to travel too far and lose its place; too narrow breaks reading rhythm. The comfortable range is 45–75 characters per line, with 66 as the widely cited optimum.
Where it comes from
It rests on typography research going back to the 1880s, formalised in Robert Bringhurst's canonical The Elements of Typographic Style, which puts the comfortable range for body text at 45–75 characters per line, with 66 the most-cited ideal.
Why it matters for your website
Typography research going back to the 1880s and formalised by Robert Bringhurst's canonical Elements of Typographic Style identifies the optimal line length for body text as 45–75 characters per line, with 66 characters the most widely cited ideal. The mechanism is physiological: the eye moves in rapid jumps (saccades) of 6-9 characters and must return accurately to the start of the next line. Lines that are too long increase the distance of that return movement, causing readers to lose their line, reread, or abandon. WCAG 2.1 codifies this as an accessibility requirement: SC 1.4.8 specifies a maximum of 80 characters per line for accessible text presentation. On modern widescreen monitors, unconstrained full-width text containers routinely produce lines of 120+ characters — a violation that is measurable in seconds and directly observable without any user testing.
The mechanism is physiological, not aesthetic. The eye reads in rapid jumps of a few characters and has to return accurately to the start of the next line; when lines are too long, that return journey lengthens, and readers lose their line, reread, or give up.
Modern widescreen monitors make this an easy mistake. An unconstrained, full-width text container routinely produces lines of 120-plus characters — well beyond the comfortable range and past WCAG 2.1's 80-character maximum (SC 1.4.8). It's a problem you can measure in seconds, without any user testing.
Wrong vs right
Body text in a full-width container on a wide monitor, running 120+ characters per line.
Text constrained to a comfortable measure — roughly 45–75 characters per line.
Lines so long the eye loses its place returning to the next line, causing rereading.
A line length that lets the eye return accurately and keep its reading rhythm.
Ignoring line length because the text is technically readable, and breaching WCAG's 80-character limit.
A max-width that keeps lines within the accessible, comfortable range.
Understanding Line Length (Measure)
Line length — typographers call it the 'measure' — is how many characters sit on a line of body text, and it has a comfortable range backed by over a century of research: 45–75 characters per line, with 66 the most widely cited ideal, formalised in Bringhurst's Elements of Typographic Style. Too wide and the eye struggles; too narrow and the reading rhythm breaks.
The reason is physiological. The eye reads in rapid jumps (saccades) of roughly six to nine characters, and at the end of each line it has to sweep back and land accurately on the start of the next. When lines are too long, that return movement covers more distance and is more error-prone — so readers lose their line, reread, or abandon the text altogether.
On modern widescreens this is a common, easily-fixed failure. An unconstrained full-width container routinely produces 120-plus-character lines, well past the comfortable range and past WCAG 2.1's 80-character maximum (SC 1.4.8) — a violation measurable in seconds, without any user testing. The fix is a simple max-width on text. It connects to scannability, plain language, and accessibility.
How Kweri checks it
Line length is one of the most directly measurable typography principles, and Kweri assesses it precisely: it can measure the characters-per-line of body text as rendered and flag lines that exceed the comfortable range or breach WCAG 2.1's 80-character maximum. There's little judgement involved — the metric is objective and observable in the rendered page. So Kweri reliably catches over-wide measures and points to the simple fix (constraining text width), making this one of the clearer automated checks rather than a heuristic one.
FAQ
What is the ideal line length for body text?
Around 45–75 characters per line, with 66 the most widely cited ideal. This range, formalised in Bringhurst's Elements of Typographic Style, keeps reading comfortable. Too wide strains the eye; too narrow breaks reading rhythm.
Why does line length matter?
Because of how the eye reads. It moves in small jumps and must return accurately to the start of each new line. Lines that are too long make that return harder, so readers lose their place, reread, or abandon the text.
What does WCAG say about line length?
WCAG 2.1 Success Criterion 1.4.8 specifies a maximum of 80 characters per line for accessible text presentation. Lines longer than that, common on unconstrained widescreen layouts, are an accessibility violation.
How do I fix lines that are too long?
Constrain the width of text containers with a max-width, so body text stays within roughly 45–75 characters per line. On wide monitors, full-width text routinely exceeds 120 characters, so a width limit is usually all that's needed.
What is 'measure' in typography?
Measure is the typographic term for line length — the number of characters on a line of text. A comfortable measure (45–75 characters) supports easy reading; too long or too short a measure disrupts it.
Related principles
People scan web pages rather than read them — structure content so scanners still get the point.
Plain, direct language is understood faster and trusted more — jargon and complexity are barriers.
The brain has a limited processing budget — demand too much and performance collapses.
Attribution & sources
Identified by Robert Bringhurst (with WCAG 2.1). Catalogued from W3C — WCAG 2.1 Understanding SC 1.4.8: Visual Presentation.
Typography research formalised by Bringhurst and codified in WCAG 2.1 SC 1.4.8; the linked W3C page is the reference used here.
See Line Length (Measure) on your own site
Run a free Kweri audit — a plain-English review of your site’s speed, accessibility, SEO and design, ranked by what to fix first. No login, no jargon.
Run a free audit →