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: line length and font size. And they’re connected. Getting one right without the other still leaves your blog hard to read.
This post is about that connection and why most blogs are worse than they need to be because of it.
The numbers, briefly
Typography research has been consistent for decades on these ranges:
- Optimal line length: 50–75 characters per line (including spaces). 66 is the bullseye.
- Desktop body font: 18–22px. 18 is the floor, not the ceiling.
- Mobile body font: 16–18px. Anything smaller fails on phones.
- Line height: 1.5 to 1.7x font size.
These aren’t arbitrary. They come from decades of typographic research on how the eye scans text. Lines that are too long make it hard for the eye to find the start of the next line. Lines that are too short break the 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 this is. After about 80 characters, eyes start mis-targeting and readers lose their place. They re-read lines, skip lines, or just bounce.
Too-short lines have the opposite problem: too many jumps. Reading rhythm gets choppy. The brain can’t settle into the prose.
The 50–75 character range is the comfortable middle where the eye glides.
Why font size matters more than people realize
Blogs commonly use 14px or 15px body text because it “looks more designed.” It doesn’t. It just makes the blog harder to read, especially for anyone over 35, anyone with imperfect vision, and anyone on a phone at arm’s length.
18px isn’t large. It’s the comfortable floor for body text on modern screens. The good blogs of the last decade have been quietly creeping their body font sizes up. Medium uses around 20px. The New York Times uses around 19px. Bloggers who use 14px are designing for designers, not readers.
The interaction that breaks blogs
Here’s the part most blogs get wrong: line length and font size scale together.
If you use a 14px body font, you can fit more characters in the same physical width than if you use a 20px font. So a blog with 14px text on a full-width container ends up with 120 characters per line, which is too long. A blog with 20px text in the same container might be around 70 characters, which is fine.
This is why “just make the font bigger” is incomplete advice. You also need to constrain the container width.
The settings that actually work
For most blogs, this combination is comfortable:
- Content container width: 700–760px maximum.
- Desktop body font: 18–20px.
- Mobile body font: 16–18px (often the same number; mobile width is naturally constrained).
- Line height: 1.6 to 1.7x.
- Paragraph spacing: roughly the same as the line height.
This produces roughly 65–75 characters per line on desktop. The result is text that’s comfortable to read for 10 minutes straight without strain.
The mistakes that show up everywhere
Full-width content
Posts that fill the entire screen width with text are exhausting. Lines hit 100+ characters and the eye fatigues fast.
Tiny body text
14px body text on a high-DPI laptop looks fine to the designer. It’s tiny on a phone and tiny to anyone over 40.
Heavy headings, light body
Some themes pair big bold headings with thin gray body text. The contrast looks elegant in a screenshot and is painful to read for 2000 words.
Tight line height
Line height under 1.5 makes paragraphs feel claustrophobic. The eye can’t easily track from one line to the next.
Inconsistent sizing across breakpoints
A post that’s 18px on desktop and 13px on mobile because of “responsive scaling” is failing on the device most readers actually use.
How to test your blog
Three quick tests:
- Read a post out loud. Where do you stumble? Where do your eyes lose place? Those are the typography problems.
- Read it on a phone, at arm’s length. Squinting? Too small.
- Measure your character count. Open a long paragraph and count the characters in a single line. Aim for 65–75. Over 85? Container is too wide. Under 50? Container is too narrow.
How themes affect this
Some themes expose container width and font sizes as customizer options. Some hard-code them. When picking a theme, this is worth checking. A theme with comfortable typography defaults saves you ever having to think about this. A theme with tiny body text and full-width containers fights you forever, even after you tweak the CSS.
This is one of the quieter reasons theme choice matters. The defaults are doing a lot of work for the 90% of bloggers who never customize them.
The short version
Line length and font size are connected. Comfortable reading sits at 50–75 characters per line, with body text at 18–20px on desktop and 16–18px 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.
