Blog · Typography
Line length and dyslexia — how many characters per line is best?
Most dyslexia reading advice focuses on font choice. Line length — how wide a column of text is — gets far less attention, yet it may be doing more damage to your reading than the wrong typeface. The fix is often simpler too: shrinking a text block from full browser width to roughly 65 characters wide can make a measurable difference to how far your eyes can travel before losing the line.
The short answer
Aim for 60–70 characters per line (including spaces). The British Dyslexia Association's style guide, the Web Content Accessibility Guidelines (WCAG 2.1), and most typographic research on reading difficulty converge on this range. Very short lines (under 45 characters) also cause problems — they force too many line breaks and disrupt reading rhythm. The sweet spot for dyslexic readers sits between about 50 and 70 characters per line.
Most websites you visit are far wider than this. A full-screen browser window on a desktop monitor can push lines past 120 characters. That's roughly twice the recommended maximum.
What line length actually means
Typographers call line length the measure. It's usually expressed either in characters per line (CPL) or in physical units (em, ch, px). For practical purposes, the most useful unit on the web is ch — one ch equals the width of the "0" character in the current font, so max-width: 65ch on a paragraph keeps lines at roughly 65 characters regardless of font size.
The reason CPL matters more than physical width is that it tracks with the thing that tires your eyes: how many fixation points your eye must make per line, and how far it has to jump at the end of each line to find the start of the next one.
Why long lines are particularly hard for dyslexic readers
Reading is not a smooth left-to-right glide. Your eyes jump in rapid hops called saccades, landing at fixation points roughly every 7–9 characters, and they occasionally flick back to re-read something (regressions). At the end of each line, your eye must execute a return sweep — a long jump from the far right margin back to the start of the next line.
For most readers, the return sweep is automatic and accurate. For many dyslexic readers, it is not. The eye lands on the wrong line, either one line above or one below the correct target, and the reader has to consciously search for where they were. This is one reason dyslexic readers lose their place so frequently — it is not always a comprehension problem, it is often a navigation problem caused by a column of text that is simply too wide.
Several factors make this worse on long lines:
- The longer the line, the longer the return-sweep saccade, and the less accurate it is.
- Wide lines make all lines look more similar, giving the eye fewer visual anchors to distinguish "the line I just read" from "the line below it."
- Wide lines increase the probability that a word at the end of line N is close in position to a word at the start of line N+1, causing the reader to accidentally skip a line entirely.
- Long lines also correlate with fewer paragraph breaks, so there are fewer rest points where the reader can re-orient.
The overlap with reading fatigue is significant. Navigating a wide column takes more cognitive effort per page, so readers tire faster and comprehend less even before they have misread anything.
What the research says
Research on line length and dyslexia is less abundant than research on font choice, but the direction of results is consistent.
Studies on general reading populations have long established that the optimal measure for comfortable silent reading is around 52–80 characters per line, with most adults settling near 65. Work specifically on dyslexic populations tends to find the lower end of this range more beneficial: shorter lines reduce return-sweep error rates and improve subjective comfort, even when reading speed does not change dramatically.
A 2012 study by Zorzi and colleagues (University of Padua) examined how letter spacing affected dyslexic readers' accuracy. While that study focused on spacing rather than measure, it noted that all conditions produced larger accuracy gains when text was presented in narrower columns — the researchers speculated that narrower columns reduced the number of competing characters in peripheral vision during each fixation, a phenomenon sometimes called visual crowding.
Visual crowding is worth understanding. When your eye fixates on a word mid-line, it is simultaneously processing the characters on either side in peripheral vision. In a wide column, more characters compete for that peripheral processing bandwidth. For readers whose visual system already finds letter discrimination harder — a common feature of dyslexia — extra crowding adds noise. A narrower measure directly reduces the field of competing characters.
The British Dyslexia Association's style guide has recommended 60–70 CPL for dyslexic readers since at least 2012, and that figure has been adopted by accessibility frameworks including the UK government's design system and the European Accessibility Act guidance materials. WCAG 2.1 Success Criterion 1.4.8 specifically allows users to limit text block width to 80 characters (it treats 80 as the maximum; 65 as better practice).
Seeing it for yourself
The difference between a well-measured and poorly-measured line is easier to feel than to describe. Here are the same two sentences at three different widths:
Most readers find the middle version noticeably easier to track — the return sweep feels automatic rather than effortful. The very narrow version creates a different problem: too many hyphenations and broken phrases, which disrupt the chunking your brain relies on to parse meaning without reading every letter.
How line length interacts with font size
Line length and font size are linked. If you increase your font size without changing the column width, lines automatically contain fewer characters — the ch-based measure shrinks naturally. This is why increasing browser zoom is often recommended for dyslexic readers: it simultaneously enlarges letterforms (easier to distinguish), reduces line length (shorter return sweeps), and increases line height relative to the page (more visual separation between lines).
The interaction also runs the other way. Using a larger font size to reduce effective line length is a useful strategy when you cannot control the column width directly — which is often the case on websites you don't own.
Line length and line spacing work together
A short line helps the return sweep land accurately, but line spacing determines how easy it is to distinguish between adjacent lines during that sweep. The two settings are complementary: narrow your measure and increase your leading, and the return sweep error rate drops substantially.
The BDA recommends 1.5× line spacing (CSS line-height: 1.5) as a minimum for dyslexic readers; some practitioners prefer 1.6–1.7× for body text. This is the same range that most modern browser reader modes default to, which is why reader mode often feels immediately more comfortable for dyslexic readers even before any font is changed. For more on what word spacing and letter spacing settings actually help, that post covers the research in detail.
The two-column problem
Newspaper-style two-column layouts are a special case. When a desktop site uses two columns, each column is narrow — sometimes usefully so. But when the content switches between columns mid-article, or when advertising interrupts the flow, the reading path becomes unpredictable. For most dyslexic readers, a single narrow column beats two columns of the same aggregate width. Our post on two-column layouts and dyslexia goes into why this is and what to do about it.
Fixing line length in your browser
You cannot change another website's CSS directly — but you have several tools that effectively control the measure you read at.
Browser zoom
The bluntest but most reliable tool. Pressing Cmd + (Mac) or Ctrl + (Windows/Linux) enlarges everything on the page. On a fixed-layout site that doesn't reflow its columns, this will eventually push the text past the viewport edge and require horizontal scrolling — at which point you have gone too far. On a responsive site (most modern sites), zoom simply reduces the effective measure and increases leading, both of which help. See browser zoom and text scaling for the full approach.
Reader mode
Every major browser ships a reader mode (Firefox Reader View, Safari Reader, Edge Immersive Reader) that strips the page down to its text content and renders it in a single narrow column — typically 60–80 CPL depending on your font size setting. For articles and blog posts, enabling reader mode is the fastest way to get good line-length control. The downside is that it strips images, tables, code blocks, and interactive elements, so it does not work well on documentation, forms, or data-heavy pages.
Font override extensions
LexiFont applies your preferred font to every page in Chrome, but it does not change column widths by itself. However, because LexiFont lets you increase the base font size site-wide, it indirectly reduces the effective measure on any site that sets column widths in px rather than ch or em. Pairing a slightly larger font (say, 18–19 px base instead of the typical 16 px default) with a dyslexia-friendly typeface like Atkinson Hyperlegible often brings line length into a comfortable range on most editorial sites. LexiFont Pro gives you per-site control over font size so you can dial this in for the sites you read most.
Custom CSS injectors
For technically confident users, a user-CSS extension (Stylus is the most maintained option as of 2026) lets you write p, li, td { max-width: 65ch !important; } as a global rule. This will misfire on some sites — narrow sidebars, code blocks, and tables do not respond gracefully to a blanket max-width — but for article reading on a small set of known sites it works well. If you want to change font and layout on any website in Chrome, that post walks through the safest approaches.
What "good" looks like: a practical target
Rather than counting characters manually, a rough visual test works almost as well: if you can hold a finger vertically at the left margin and reach the other side without your arm extended past a relaxed position, the line is probably too long. A more calibrated heuristic: if a typical line of body text is noticeably wider than the text of this article (which sits at around 65 CPL), you are reading at an unfriendly measure.
The target settings for comfortable dyslexic reading, combining measure with the related parameters:
- Line length: 60–70 characters per line (CSS
max-width: 65chon body text) - Line height: 1.5–1.7× (CSS
line-height: 1.6) - Font size: at least 14pt / 18px for body text — see font size guidance for dyslexic adults
- Text alignment: left-aligned, never justified — justified text creates uneven word gaps that compound the crowding problem
- Letter spacing: at least 0.05em above the font default
On the dyslexia-friendly web design checklist, this combination is the single highest-impact cluster of settings — more reliable in practice than font choice alone.
A note on mobile
On mobile, line length is almost never the problem. A 375 px wide screen at 16 px base size gives roughly 23 characters per line — far too narrow, which is why most mobile sites use a slightly larger base size (17–18 px) and allow generous white space. Reading on mobile with dyslexia involves different trade-offs; the line-length problem is primarily a desktop concern.