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Best font size for dyslexic adults
The default body size on the web is 16 pixels. Most accessibility advice you'll find tells you to "use a larger font" without naming a number. That's not actionable. This piece does the opposite — it gives you a specific size range that the research and reader reports converge on for dyslexic adults, explains why the unit you set the size in matters more than the number, and shows you how to apply the result to every site you read.
The short answer
For most dyslexic adults reading on a screen, the comfortable range is 18 to 22 pixels for body text — with 20 px as a sensible default starting point.
That's noticeably larger than the web's 16 px default, but smaller than the "make it huge" advice you sometimes see. Below 16 px, error rates climb for almost everyone. Above 24 px, line lengths shrink so much that you spend more time wrapping than reading. The 18–22 band is the practical sweet spot.
If you want a single number to type into your browser settings: 20 pixels. Read for a week. If words still feel cramped, push to 22. If lines are wrapping every six or seven words on long-form sites, drop to 18.
Why "best font size" is the wrong question on its own
Font size in isolation doesn't determine readability. Three other variables travel with it, and changing one without the others usually fails:
- Line height (leading) — must scale with size. A 20 px font set on 1.2 line-height looks denser than a 16 px font on 1.6.
- Line length (measure) — the comfortable target is 50–75 characters per line. Larger fonts on a fixed-width container reduce characters per line; this is good up to a point and harmful beyond it.
- Typeface choice — different fonts at the same nominal size have very different x-heights. Lexend at 18 px reads roughly the size of Times New Roman at 20 px.
Picking a size without thinking about line height and typeface is like buying shoes without knowing the sock thickness. We'll come back to all three.
What the research suggests
The most cited published work on font size and dyslexia is by Luz Rello and Ricardo Baeza-Yates, whose 2013 and follow-up studies tested dyslexic readers across a grid of font sizes, fonts, and line spacings. The headline finding: larger sizes consistently improved reading comfort and reduced fixation duration, with the gains flattening out around 18–22 pt on print and 18–22 px on screen. Going to 26 pt or 28 pt didn't continue to help; it tended to fragment lines into too-few words.
British Dyslexia Association style guidance, which is referenced in many institutional accessibility policies, recommends a body text minimum of 12–14 pt for print — but explicitly notes that the screen equivalent is larger because of viewing distance and pixel density. Their general recommendation for screens is "16 px or larger," which is a floor rather than a target.
The pattern across these sources is consistent: the floor is around 16 px, the comfort zone is 18–22 px, and gains flatten out beyond about 24 px. None of these sources promise dramatic speed improvements from size alone — what they document is reduced effort, fewer regressions (eye flicks back to re-parse a word), and longer sessions before fatigue.
See it for yourself
Below is the same paragraph at five sizes. The font is Atkinson Hyperlegible — the typeface this site uses. If you're a dyslexic adult, you'll probably feel one of these as the right one within a sentence or two. That gut feel is more diagnostic than any chart.
Pixels, points, ems — which unit should you set?
This is the part most articles skip, and it's the reason "I changed my font size and the site looked the same" is such a common complaint. Different units behave differently when websites or applications scale, zoom, or override defaults.
| Unit | Best for | Behaviour |
|---|---|---|
| px (pixels) | Browser overrides, extensions | Absolute. The site can ignore it if its CSS uses fixed sizes. |
| pt (points) | Word, Google Docs, PDFs | Print convention. 1 pt ≈ 1.33 px on screen at 100% zoom. |
| em / rem | CSS authors, not end users | Relative. Inherits from parent / root size; respects user defaults. |
| % (percent) | Browser settings, OS-level scaling | Relative to the user's default; scales the whole UI proportionally. |
For day-to-day reading, the two units that matter are px (when you're forcing a size on a website) and pt (when you're configuring Word, Google Docs, or a PDF reader). The mental conversion is simple: multiply points by 1.33 to get pixels. So 14 pt in Docs ≈ 18.6 px on screen — comfortable. 11 pt (Word's default) ≈ 14.7 px — too small.
If you're configuring a writing surface, our dyslexia-friendly Google Docs setup walks through exactly which size to choose, in points, and pairs it with the right line height and page colour.
Pairing size with the right typeface
Two fonts at the same nominal size can read very differently because their x-height — the height of lowercase letters relative to the cap height — varies. Lexend, designed by Bonnie Shaver-Troup specifically around reading-rate research, has a generous x-height and looks larger at any given size than fonts like Times New Roman or Garamond. OpenDyslexic also has a tall x-height with the additional weighted-bottom glyphs.
Practical implication: if you switch from a default site font to a dyslexia-friendly font, you may need to drop your size by 1–2 px. 20 px Times New Roman and 18 px Lexend look about the same on the page. You'll know within a paragraph whether you've over- or under-scaled.
If you're new to choosing between dyslexia-friendly fonts, start with our best fonts for dyslexia in 2026 guide — it ranks the five typefaces most often recommended for dyslexic adults and explains where each one shines.
Setting your default in Chrome
Chrome's built-in font-size control is the single most underused setting in browser accessibility. Here's how to use it well:
- Open
chrome://settings/fontsin a new tab. - Drag the "Font size" slider — the centre is "Medium" (16 px). One notch right is "Large" (20 px). That's usually where dyslexic adults want to be.
- Drag "Minimum font size" up to 14 or 16 px. This is the size below which Chrome refuses to render any text — a hard floor for sites that try to use 11 px legalese.
The catch: many websites use absolute pixel sizes in their CSS, which Chrome's slider doesn't override. The slider sets your default, but if a site explicitly sets font-size: 14px, you'll still see 14 px there.
For the sites that ignore your default, you have two options:
- Page zoom (Ctrl/⌘ +) — quick, but enlarges images, layout, and gaps along with the text. Works on any site.
- A user stylesheet or override extension — applies a forced minimum to every site, more surgical than zoom. Our guide to changing fonts on any website in Chrome covers the five mechanisms in detail.
The line-length trap
The most common failure mode after increasing size is forgetting line length. If you bump body text from 16 px to 22 px without changing the page width, line length drops from a comfortable ~70 characters to ~50, and on narrow content columns it can drop into the 30s — short enough that you spend more time hopping to the next line than reading the current one.
Two fixes:
- Reader mode (Chrome's "Reading Mode" or any extension that strips a page to its article) usually fixes line length automatically by setting a max-width. Many dyslexic adults find that combining reader mode with a 20 px override is more comfortable than tweaking the live site.
- Browser zoom on a wide window. Counter-intuitively, if your monitor is wide, zooming the page often improves line length because the layout reflows to fill the window.
Don't forget line height
Increase font size, increase line height. The British Dyslexia Association suggests 1.5× the font size as a line-height target — so 20 px text wants roughly 30 px line height. The web's default is around 1.2, which is too tight at any size for sustained reading by a dyslexic reader.
The full set of spacing tweaks — line height, letter spacing, word spacing — interact in non-obvious ways. We've written a separate, opinionated piece on the numbers we recommend in line spacing and letter spacing for dyslexia — what actually matters.
Edge cases
Reading on a phone
The pixel-density story changes on mobile. iOS and Android measure "points," not raw pixels, and one point is two or three physical pixels on a Retina/OLED display. The accessibility setting you want on iPhone is Settings → Display & Brightness → Text Size, plus Larger Text in Accessibility → Display & Text Size for going past the slider's normal max. On Android, Settings → Display → Font size and Display size together cover it. The 18–22 px screen target translates roughly to "one or two notches above the default" on most phones.
Reading at distance
If you read on a TV or a wall-mounted monitor at 1.5 metres or more, every recommendation in this article scales with distance. Rule of thumb: the smallest comfortable text height should subtend at least 0.3° of visual angle, which at a metre is about 5 mm. At 2 metres, double it.
If the site won't budge
A surprising number of sites — particularly older newspapers, government portals, and forum software — set body text at 13 or 14 px and resist overrides. For these, the most reliable answer is a font-and-size override extension. LexiFont Pro includes per-site size, font, and contrast overrides exactly because of these stubborn cases.
A 90-second self-test
You don't need to commit. Here's a quick way to find your number:
- Open a long-form article you've been meaning to read (a Wikipedia entry works).
- Press Ctrl/⌘ + once. Read the first paragraph. Note effort.
- Press Ctrl/⌘ + once more. Read the second paragraph. Note effort.
- Repeat until reading feels easy. Note the zoom level (Chrome shows it at the right of the address bar).
Whatever zoom level felt right multiplied by 16 px gives you your default-equivalent. 110% × 16 = 17.6 px. 125% × 16 = 20 px. 150% × 16 = 24 px. Set Chrome's default font size and your OS-level text size accordingly, and you'll experience that comfort everywhere instead of one tab at a time.
If, after the test, you find the right comfort comes from a smaller size in a more legible typeface — Lexend, Atkinson Hyperlegible, or OpenDyslexic — rather than a larger size in the default font, that's worth knowing too. LexiFont applies a dyslexia-friendly font to every site you visit; combining a font override with a 18–20 px size is, for most readers, a stronger move than either alone.
Get LexiFont Pro — per-site font, size, and spacing overrides for $14.99 one-time