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Best font size for dyslexic adults
If you ask a dyslexic adult what would make web reading easier, "make the text bigger" is almost always the first answer. It's not wrong - but it's incomplete. Font size interacts with line height, letter spacing, line length and font choice in ways that mean a single number is rarely the right answer. Here's what the research actually recommends for adult dyslexic readers, why over-sizing backfires, and the exact settings to apply in your browser.
The short answer
For body text on a desktop screen, target 18-22px (roughly 1.125-1.375 rem) with line height 1.5 and a measure of 60-75 characters per line. That range outperforms the default 16px in nearly every dyslexia-related study, without crossing into the "too big" territory where lines wrap awkwardly and the eye loses its place at the end of each line.
For headlines and short snippets, you can go bigger. For long-form reading, the size only helps if the line length and line spacing scale with it.
What the research actually says
The most-cited figure in this space comes from the British Dyslexia Association's style guide, which recommends 12-14pt for print. Translated to the screen at standard browser DPI, that lands close to 16-19px. Other accessibility guidance tends to bracket the same range: the WCAG resize-text criterion treats 16px as a floor rather than a target, and most modern reading research with dyslexic adults uses test sizes between 18px and 24px.
Two findings recur across the studies that matter:
- Bigger helps - up to a point. In controlled studies, dyslexic adults typically read faster and with fewer regressions at 18px than at 12-14px. The benefit plateaus somewhere around 22-24px. Past that, reading speed often drops, because lines wrap to so few words that the eye has to make many more downward jumps per paragraph.
- Size cannot compensate for crowding. Larger letters help only if the white space around and between them scales accordingly. A 22px font with default tight line height (1.2) and 100-character lines often performs worse than a well-tuned 16px setup. See our companion piece on line spacing and letter spacing for dyslexia for the numbers there.
See the difference
Why over-sizing backfires
The intuition that "bigger is always better" comes from poster reading, where one or two words appear at a time. Long-form reading is different. Two specific failure modes show up when font size goes past about 24px on a typical laptop screen:
Short lines force more vertical jumps. A typical article column is around 700-800 pixels wide. At 16px the same column holds roughly 12 words per line; at 28px it holds 6-7. Reading the same paragraph means twice as many line breaks, twice as many downward eye movements, and twice as many opportunities to skip a line or re-read one. For dyslexic readers who already struggle to track lines, this is the opposite of what you want.
Line height stops scaling. Most websites use a line-height value pinned to the font, like line-height: 1.4. When you bump font size with the browser zoom or a user style, that ratio holds. But the eye doesn't scale linearly - the gap between lines that "feels right" at 16px doesn't quite scale to 28px, and lines start to feel cramped vertically even though the absolute pixel gap is larger. This is one of the reasons "browser zoom" alone (Ctrl + +) often feels worse than a real font setting that controls size and spacing independently.
Font size interacts with font choice
The same point size renders very differently across fonts. Two fonts at "18px" in CSS can look almost a step apart visually, because point size measures the em-box height rather than the actual letter height. Atkinson Hyperlegible and Lexend both have a relatively large x-height, so they look bigger at the same px setting than, say, Times New Roman or Garamond. OpenDyslexic is somewhere in between, but its weighted bottoms add visual weight that compensates for it.
Practically, this means:
- If you switch from a default site font to Atkinson Hyperlegible, you can often drop the size by 1-2px and still feel like the text "looks bigger."
- If you switch to Lexend, the same rule applies - it's a tall x-height font tuned for readability at smaller sizes.
- If you use OpenDyslexic, keep the size on the larger side of the recommended range. The weighted-bottom shapes need a bit more space to breathe.
The line-length question
Font size only does its job if the line length follows. The classic typographic rule is 45-75 characters per line for body text; for dyslexic readers, the upper end of that range (60-75) tends to work best. Below 45 characters, you get the "too many short lines" problem above. Above 80 characters, the eye loses its place returning to the start of the next line.
You can quickly check the measure on any page: count the characters in a typical line of body copy. If you're at 100+ characters and reading feels effortful, narrowing the column will usually do more for you than bumping the font size.
Recommended starting settings
| Setting | Recommended value | Why |
|---|---|---|
| Font size | 18-22px | Above the comfort floor, below the line-wrap penalty |
| Line height | 1.5 | The standard WCAG and dyslexia-research recommendation |
| Letter spacing | +0.04 to +0.06 em | Modest tracking has a measurable reading-speed benefit |
| Line length | 60-75 characters | Enough words per line to flow, few enough that the eye doesn't lose the next line |
| Font | Atkinson Hyperlegible, Lexend, or OpenDyslexic | Pick the one that matches your specific reading issue (see the full guide) |
| Contrast | Dark text on cream/off-white, or warm dark mode | Pure black on pure white can feel harsh at any size |
Reading distance and DPI
One subtlety the research often skips: the right pixel size depends on how far you sit from the screen and the screen's pixel density. On a 27-inch 4K monitor at desk distance, 22px looks comfortably large. On a high-DPI 13-inch laptop in your lap, the same 22px is noticeably bigger. On a 5-inch phone held 30 cm from your face, 22px might be larger than you need.
A useful rule of thumb: the lowercase x-height of body text should subtend roughly 0.3-0.4 degrees of arc at your eye - about the width of a pinky fingernail held at arm's length. If you can comfortably read the text without leaning in, you're probably close enough to the right size, regardless of the px number.
How to apply these settings to every site
Most websites ignore your wishes here. They ship at whatever size their designer chose, and browser zoom (Ctrl + +) blows up the entire layout - images, navigation, ads - rather than just the text. There are three cleaner approaches:
Browser default font size. Chrome's Settings -> Appearance -> Font size changes the base size for sites that respect it. The catch is that many modern sites pin their body text to a specific px value and ignore the browser default entirely. Useful as a baseline; not a complete solution.
Reader mode. Chrome's built-in reader mode strips a page down to its main content and lets you set font, size, and theme. It's excellent for long articles, but only works on pages it recognises as "article" content - so it's no help for inboxes, dashboards, or wikis.
A font-override extension. This is the only approach that handles every site uniformly. LexiFont applies your chosen font, size, line height, and letter spacing to every page automatically. You set 20px once and every site you visit renders body text at 20px - including Gmail, Notion, GitHub, news sites, and the parts of pages reader mode can't reach.
The honest test: set your size somewhere in the 18-22px range, leave it there for a week, and notice how often you reach for the zoom keyboard shortcut. If your hand stops moving toward Ctrl+, you've found your number. If it doesn't, nudge by 2px and try again.
Get LexiFont Pro - apply your size, font, and spacing to every website for $14.99 one-time
Further reading
- Best fonts for dyslexia in 2026 - a research-first guide
- Line spacing and letter spacing for dyslexia - what actually matters
- Serif vs sans-serif for dyslexic readers - what the research says
- Dyslexia-friendly dark mode - does inverted contrast actually help?
- How to change the font on any website in Chrome