Typography arguments online focus on the wrong things: which fonts are best, which weights to use, whether to underline links. Meanwhile two settings that affect readability more than any of those go ignored almost entirely: line length and font size. The two are connected in a way most people never think about. Getting one right without the other still leaves your blog hard to read.
This post is about that connection and why so many blogs are worse to read than they need to be because of it.
The numbers, briefly
Typography research has been consistent for decades on these ranges:
- Optimal line length: 50 to 75 characters per line, including spaces. Around 66 is the bullseye most researchers converge on.
- Desktop body font: 18 to 22px. 18 is the floor, not the ceiling.
- Mobile body font: 16 to 18px. Anything smaller tends to fail on phones.
- Line height: 1.5 to 1.7 times the font size.
These ranges aren’t arbitrary. Baymard Institute’s research on line length confirms the same pattern that typographers have argued for decades: lines that run too long make it hard for the eye to find the start of the next line, and lines that are too short break the natural rhythm of reading.
Why line length matters more than people realize
The eye scans a line of text in a left-to-right sweep. When the line ends, the eye needs to find the start of the next one. The longer the line, the harder that jump becomes. Past roughly 80 characters, eyes start mis-targeting and readers lose their place. They re-read lines, skip lines, or just bounce around the paragraph without settling in.
Lines that are too short create the opposite problem: too many jumps in quick succession. Reading rhythm gets choppy, and the brain never quite settles into the prose the way it does at a comfortable measure.
The 50 to 75 character range is the comfortable middle where the eye glides across the page instead of fighting it.
Why font size matters more than people realize
Blogs commonly use 14px or 15px body text because it “looks more designed” on a desktop monitor. It doesn’t actually look better. It just makes the blog harder to read, especially for anyone over 35, anyone with imperfect vision, and anyone reading on a phone at arm’s length.
18px isn’t a large size. It’s the comfortable floor for body text on modern screens. The strongest publishing sites of the last decade have been quietly increasing their body font sizes for years. Medium uses around 20px. The New York Times uses around 19px. Bloggers who ship 14px body text are designing for other designers, not for the people actually reading their posts.
The interaction that breaks blogs
Here’s the part most blogs get wrong: line length and font size scale together, and treating them separately is where the trouble starts.
A smaller body font fits more characters into the same physical width than a larger one does. So a blog running 14px text in a full-width container can easily end up with 120 characters per line, which is far too long to read comfortably. The same container with 20px text might land around 70 characters, which sits right in the comfortable range.
This is why “just make the font bigger” is incomplete advice on its own. You also need to constrain the container width, or the bigger font just makes the same overlong lines slightly less overlong.
The settings that actually work
For most blogs, this combination produces genuinely comfortable reading:
- Content container width: 700 to 760px maximum.
- Desktop body font: 18 to 20px.
- Mobile body font: 16 to 18px, often the same number, since mobile width is naturally constrained already.
- Line height: 1.6 to 1.7 times the font size.
- Paragraph spacing: roughly the same as the line height.
This produces roughly 65 to 75 characters per line on desktop. The result is text that stays comfortable to read for ten minutes straight without any real strain.
The mistakes that show up everywhere
Full-width content
Posts that fill the entire screen width with unconstrained text are exhausting to read. Lines hit 100 or more characters and the eye fatigues fast, even on genuinely interesting writing.
Tiny body text
14px body text on a high-DPI laptop can look fine to the person designing it. It reads as tiny on a phone, and tiny to anyone over 40 regardless of screen.
Heavy headings, light body
Some themes pair big bold headings with thin gray body text. That contrast looks elegant in a screenshot and turns painful to read across 2,000 words of actual content.
Tight line height
Line height under 1.5 makes paragraphs feel claustrophobic. The eye can’t easily track from the end of one line to the start of the next.
Inconsistent sizing across breakpoints
A post that’s 18px on desktop and 13px on mobile because of aggressive “responsive scaling” is failing on the exact device most readers actually use to read it.
How to test your blog
Three quick tests catch most problems:
- Read a post out loud. Notice where you stumble and where your eyes lose their place. Those are the typography problems worth fixing first.
- Read it on a phone, at arm’s length. If you’re squinting, the text is too small for how people actually hold their phones.
- Measure your character count. Open a long paragraph and count the characters in a single line. Aim for 65 to 75. Over 85 means the container is too wide. Under 50 means it’s too narrow.
How themes affect this
Some themes expose container width and font sizes as Customizer options you can adjust freely. Others hard-code them, which means you’re stuck with whatever the developer chose. When picking a theme, this is worth checking directly rather than assuming. A theme with comfortable typography defaults saves you from ever having to think about this again. A theme with tiny body text and full-width containers fights you forever, even after you tweak the CSS by hand.
Aurora exposes both pieces of this equation as real Customizer controls rather than baked-in values: responsive font sizing for desktop, tablet, and mobile independently, plus a site width setting that lets you constrain the content column to a comfortable measure without editing code. Getting line length and font size right shouldn’t require a developer, and it doesn’t have to.
This is one of the quieter reasons theme choice matters as much as it does. The defaults are doing a lot of work for the 90 percent of bloggers who never touch them. If you’re still comparing options, our post on what white space actually does in a layout covers the closely related question of spacing around that same text.
Two settings, one reading experience
Line length and font size are connected. Comfortable reading sits at 50 to 75 characters per line, with body text at 18 to 20px on desktop and 16 to 18px on mobile. Container width and font size together determine your character count. Get both right and your blog feels effortless to read. Get one right and the other wrong and the blog still feels off, in a way readers can’t quite name.
