Blog · Fonts

Calibri and dyslexia

10 min read · July 12, 2026

Calibri has been on more screens than almost any other font. Microsoft made it the default for Word, Excel, and PowerPoint in 2007, replacing Times New Roman — a change that put it in front of hundreds of millions of people overnight. For most readers the switch was unremarkable. For dyslexic readers, Calibri comes with a specific set of problems worth understanding, and there are better options already installed on most computers.

What makes Calibri Calibri

Calibri is a humanist sans-serif designed by Luc(as) de Groot and released with Windows Vista and Office 2007. It was the first Microsoft Office default designed specifically for ClearType rendering — the subpixel antialiasing system that made text look sharper on LCD screens. This was a genuine advancement: Times New Roman was designed for 1930s newspaper printing and looked rough at typical screen resolutions. Calibri's soft, slightly rounded letterforms were purpose-built for the pixel grid of early-2000s monitors.

For general screen reading at the time, Calibri was a real improvement. But "better than Times New Roman on a low-resolution LCD" is a low bar, and the design choices that made Calibri appealing for screen rendering turn out to be the same ones that make it harder for dyslexic readers.

Where Calibri falls short for dyslexic readers

Condensed proportions

Calibri is noticeably narrower than Verdana or Arial. Its letters have tighter width-to-height ratios, which lets more text fit on a line — a practical advantage in documents, but a legibility cost for dyslexic readers. Wider letters mean more visual distance between confusable letterforms. The lateral spread of a 'd' makes it easier to tell apart from a 'b' when there is real horizontal space between the stem and the bowl. Calibri compresses that space.

This narrowness also affects spacing between words. Calibri's word-spacing at normal settings is tighter than fonts designed with dyslexic readers in mind. Research by Rello and colleagues has consistently shown that extra letter-spacing — around 0.1 em above a font's default — reduces reading errors for dyslexic readers. Calibri's defaults don't build that buffer in.

Modest x-height

X-height is the height of lowercase letters relative to capitals. A higher x-height increases the visible area of each lowercase letter, which matters because most reading happens in the lowercase. Fonts explicitly designed for legibility — Verdana, Atkinson Hyperlegible, Lexend — maximise x-height deliberately. Calibri's x-height is moderate rather than high, leaving lowercase letters smaller relative to the page than is ideal for readers who benefit from clear, large letterforms. See our guide to x-height and dyslexia for a fuller explanation of why this metric matters.

Two-story a and g

Calibri uses two-story forms for 'a' and 'g' — the forms you see in most printed body text. Two-story forms are not uniquely harmful, but they add visual complexity compared to single-story alternatives. A single-story 'a' looks like a circle with a tail. A two-story 'a' has a closed top bowl and an enclosed counter, creating two distinct visual regions. For readers who process letter shapes more analytically than fluently — as many dyslexic readers do — two-story forms add decoding work that single-story forms skip entirely. Lexend and Atkinson Hyperlegible both choose single-story 'a' for this reason.

Symmetrical b/d/p/q

No standard sans-serif font completely eliminates b/d/p/q confusion — these letters are geometric rotations of each other, and any design that doesn't deliberately break that symmetry will leave some ambiguity. Calibri's rounded, soft forms make these letters feel particularly fluid and interchangeable. The bowl of a Calibri 'b' and the bowl of a Calibri 'd' are nearly identical in shape; only position relative to the stem distinguishes them. Fonts that add asymmetric features — the slight flag on the stem of Atkinson Hyperlegible's 'd', or OpenDyslexic's weighted bottoms — give readers an extra perceptual hook. See our article on letter reversals for a deeper look at why this matters and which fonts address it best.

If you are reading this in a browser that has Calibri installed (any Windows machine, most Macs), the left panel above will render in Calibri. The right panel renders in Atkinson Hyperlegible via Google Fonts. Notice the differences in letter width, spacing, and the shape of 'b' versus 'd'.

How Calibri compares to the alternatives

Verdana is the most practical upgrade for most people. Designed by Matthew Carter for Microsoft in 1996 specifically for screen legibility, it has wider letterforms, a higher x-height, and clearer letter differentiation than Calibri — and it is already installed on virtually every Windows and Mac computer. If you need to stay within pre-installed fonts, Verdana is a straightforward, document-safe improvement. For a full comparison of the two see Verdana and Arial for dyslexia.

Arial is in roughly the same category as Calibri — a marginal improvement in some metrics, a lateral move in others. If you are choosing between the two, prefer Verdana rather than settling for Arial.

Atkinson Hyperlegible was designed by the Braille Institute specifically to maximise letter distinction for low-vision readers. Every letterform is drawn to be unambiguous: different shapes for I, l, 1, and i; wider proportions; deliberate asymmetries where letters would otherwise be confusable. It is free via Google Fonts. For dyslexic readers dealing with multiple types of letter confusion simultaneously, Atkinson Hyperlegible is a more deliberate solution than anything in the pre-installed Microsoft family. See our guide to the best fonts for dyslexia in 2026 for a broader survey.

OpenDyslexic addresses the rotation-confusion problem more aggressively than any sans-serif by adding visually distinct weighted bottoms to every letterform, making b/d/p/q orientation unambiguous. If letter rotation is your primary difficulty with Calibri, OpenDyslexic targets that specific problem directly. If you also find Calibri's condensed proportions tiring — even on words you are not confusing — Atkinson Hyperlegible or Verdana may be a better first choice.

A note on Aptos

Microsoft began transitioning away from Calibri as the default Office font in 2022, and rolled out the new default — called Aptos — across Microsoft 365 in 2023. Aptos is slightly wider than Calibri and has a cleaner, more neutral design. For dyslexic readers, it is a modest improvement: a touch more letter width, a touch cleaner spacing. But it is still a general-purpose corporate font rather than a legibility-first design, and it does not resolve the core issues — condensed proportions relative to purpose-designed alternatives, no special handling of confusable letters. If your Office apps now default to Aptos, the same guidance applies: Verdana is still a better choice for dyslexic readers, and Atkinson Hyperlegible or OpenDyslexic are better again.

Changing Calibri in Office desktop apps

The quickest way to change the default in Word is to open a blank document, select all text (Ctrl+A on Windows, Cmd+A on Mac), change the font in the toolbar to your preferred alternative, then click the small arrow at the bottom-right of the Styles group on the Home tab, choose "Set as Default," and save. From that point on, every new Word document will open in your chosen font.

A few practical pointers. If you share documents with people who may not have a specific font installed, Verdana is the safest choice — it is ubiquitous. If the document is for your own reading only, Atkinson Hyperlegible is available as a free download from the Braille Institute and works in any Office app once installed. Changing the default does not affect documents you have already saved; it only applies to new ones.

In Outlook for Windows, the default font for composing emails is set separately in File > Options > Mail > Stationery and Fonts. The same logic applies: Verdana 11pt or 12pt is a safe, readable choice that recipients with any operating system will see correctly.

The web layer: Teams, Outlook web, and SharePoint

The Office desktop applications are one part of the picture. The web versions of Microsoft's productivity tools — Teams web (teams.microsoft.com), Outlook.com, Outlook web access, Word Online, and SharePoint — each render text in Calibri or Aptos via CSS, which means they are websites. And websites can be overridden by a browser font extension, regardless of what Microsoft has specified.

This is where a tool like LexiFont Pro becomes directly useful. It applies a font of your choosing — Atkinson Hyperlegible, Lexend, OpenDyslexic, or any other installed font — across every website you visit, including Microsoft's web apps. The override happens in the browser, so it doesn't change what the other person receives or sees; it only changes what you see on your screen. For a step-by-step setup for Teams specifically, see reading Microsoft Teams with dyslexia. For Outlook email, see reading Outlook email with dyslexia.

Practical recommendations

If you have dyslexia and use Microsoft Office regularly, the single highest-impact change you can make is switching the Word and Outlook default from Calibri to Verdana. No download required, it works in documents you share, and it resolves most of the proportion and x-height issues in under two minutes.

If you spend significant time in browser-based Office apps — Teams, Outlook web, Word Online — adding a font-override extension takes another five minutes and applies the fix to those surfaces too. LexiFont's free tier will already help here; LexiFont Pro unlocks the full font library including Atkinson Hyperlegible and Lexend.

If letter rotation (b/d/p/q confusion) is a major part of what makes reading hard, try OpenDyslexic on web content first — it addresses that problem more directly than any proportional adjustment. The fonts handle different problems, and you may find you want Verdana in your documents and OpenDyslexic in your browser. LexiFont makes it easy to switch between them without committing to one globally. See our piece on font weight and dyslexia for more on how typographic choices interact.

Further reading

• Verdana and Arial for dyslexia — do they actually help?
• Best fonts for dyslexia in 2026 — a research-first guide
• X-height and dyslexia — why lowercase letter height matters
• Letter reversals b/d/p/q — why they happen and which fonts help
• Reading Microsoft Teams with dyslexia — font and layout fixes