Body Text Size and Line Length for Readable Service Pages
Reading studies, Baymard's usability testing, and the GOV.UK Design System point toward body text that is not too small and lines that stay under about 75 characters. Here is what the evidence supports, where it stops, and how to set line length and text size on a service website.
Most service pages are read in paragraphs, not headlines. The description of what you do, how the process works, and what it costs all sits in body text. Yet the size and width of that text are often settled by the layout grid rather than by reading needs. On a wide monitor, a full-width paragraph can run past 120 characters per line. On a phone, a design system may shrink body text to fit more on the screen.
Both decisions affect whether visitors read the copy or skip it. This article brings together peer-reviewed reading studies, Baymard Institute’s usability research, the GOV.UK Design System, and the relevant WCAG criteria to show what is actually known about line length and body text size, where the evidence is thin, and how to set both on a service website.
Why line length ends up decided by the layout
Line length, sometimes called the measure, is the number of characters in one line of text, including spaces. On the web it usually isn’t chosen directly. It’s whatever results from the container width, the font, and the font size.
That’s how long lines appear on service sites:
- Full-width sections. A “How we work” block set to the page width on a 1440-pixel screen can produce very long lines of body text.
- Builder defaults. Page builders often size text containers to the layout column, not to the paragraph.
- Shrinking on small screens. Some type scales reduce body text on phones to fit more words on each line.
Baymard Institute’s large-scale e-commerce usability testing describes what happens next. In a 2022 article, Baymard reports that users perceived long lines of text as intimidating and overwhelming, and some went straight back to the previous page rather than “get through” it. Others started reading and left without fully understanding the product or service. These are qualitative observations from usability sessions, not a controlled measurement of reading speed, but the consequence is clear: copy that isn’t read can’t explain your offer.
What the reading research measured
Line length on screens has been studied for decades, and the results are more nuanced than the “ideal measure” often quoted in design guides.
Speed and comprehension don’t always agree. In a 1998 paper in Visible Language, Mary Dyson and Gary Kipping of the University of Reading compared screen text at 25, 55, and 100 characters per line (cpl). Long lines of 100 characters were read faster than very short lines of 25, and comprehension stayed the same. Participants’ opinions didn’t match their performance, though. They rated the 100-character lines least easy to read and the 55-character lines easiest.
A medium line length supported comprehension. In a 2001 study in the International Journal of Human-Computer Studies, Dyson and Mark Haselgrove tested the same line lengths at normal and deliberately fast reading speeds. A medium length of 55 characters per line “appears to support effective reading” at both speeds. It produced the highest comprehension and was read faster than the short lines. Reading fast reduced comprehension overall.
So the case for a medium measure isn’t that it’s always fastest. It’s that it seems to balance speed, comprehension, and how comfortable reading feels. Baymard’s summary of the typographic principles points to one mechanism: the return sweep, the eye’s jump from the end of one line to the start of the next. On very long lines, it’s harder to land on the correct next line. It’s a little like looking up from a book and finding your place again: the farther the eye has to travel, the easier it is to pick up the wrong line. On very short lines, the eye travels back so often that the reading rhythm breaks.
Larger body text helped, up to a point. In “Make It Big!”, presented at ACM CHI 2016, Luz Rello, Martin Pielot, and Mari-Carmen Marcos ran an eye-tracking study with 104 participants reading Wikipedia articles in Arial at sizes from 10 to 26 points and line spacings from 0.8 to 1.8. Readability, measured by mean fixation duration (the average time the eyes pause while reading), improved significantly as font size increased. Participants answered comprehension questions correctly more often at 18 and 26 points than at 10 and 12. Gains in the objective measures stopped beyond 22 points, and participants rated 18 points the most readable. Line spacing had no effect on objective readability, but the two extremes, 0.8 and 1.8, hurt comprehension. Pielot notes that, in a standard desktop setting, 18 points corresponds to setting the browser to 24 pixels.
What these studies don’t establish
The limits matter as much as the findings:
- Lab conditions and older hardware. Rello’s study took place at the end of 2012 on a 17-inch monitor at 1024 × 768 pixels, with line length held constant. The authors say further studies are needed for tablets and phones.
- One font, one kind of text. Rello used only Arial. Its texts were short encyclopedia articles, and the comprehension questions were in Spanish. Dyson’s studies date from 1998 and 2001, before responsive layouts and today’s screens. None of the three tested service-page copy.
- Few line lengths tested. Dyson’s studies compared three line lengths, not a continuous range, so “55 characters” is the best of the conditions tested, not a measured optimum.
The evidence supports a direction: avoid very long lines, avoid small body text, and avoid extreme line spacing. It doesn’t support one exact number.
“Line length isn’t a style preference. It decides whether the paragraph that explains your service gets read.”
— Windware Studio Practice Note
How design standards turn the evidence into defaults
Usability guidelines, design systems, and accessibility standards have turned these findings into working rules, with some useful differences.
| Source | Line length guidance | Body text guidance | What kind of guidance it is |
|---|---|---|---|
| Baymard Institute (2022) | 50–75 characters, citing Emil Ruder’s 50–60 and other sources accepting up to 75 | Line length is “only one component” of readability | Usability research recommendation |
| GOV.UK Design System | Two-thirds column layout, “usually” no more than 75 characters per line | Body text 19px with 25px line height on all screen sizes | Government design system default |
| WCAG 2.2 SC 1.4.8 (Level AAA) | A mechanism to get blocks of text no wider than 80 characters (40 for Chinese, Japanese, or Korean) | Line spacing of at least 1.5 available through a mechanism | Accessibility success criterion, highest level |
| WCAG 2.2 SC 1.4.12 (Level AA) | Not specified | Content must survive user overrides: line height 1.5, paragraph spacing 2×, letter spacing 0.12×, word spacing 0.16× the font size | Accessibility success criterion, common conformance target |
The GOV.UK change is recent. GOV.UK Frontend v6.0.0, released in February 2026, made an updated type scale the default after first offering it as an opt-in in version 5.2.0. Standard body text now stays at 19px on small screens instead of dropping to 16px, and the 14px size has been removed. A 2022 Government Digital Service post explains the reasoning: service teams reported that using smaller text on smaller screens is no longer standard practice and disadvantages people with visual impairments, and that sizes of 14px and below are bad for accessibility. The post also notes that WCAG sets no minimum font size, and cites the British Dyslexia Association’s recommendation not to go below 12pt, roughly 16px.
The WCAG criteria are easy to misread in both directions. SC 1.4.8 is Level AAA, and W3C states that content isn’t required to use its values. The requirement is that a mechanism, which can be the browser, lets users get them. SC 1.4.12 doesn’t require you to set line height to 1.5 either. It requires that nothing is clipped or overlapped when a user does. GOV.UK’s own 19px/25px body style has a line height of about 1.3, which shows that the authored default and the user-adjustable range are separate decisions.
Setting line length and text size on a service site
Apply these as starting points during design, then test them with the real copy:
- Limit the text column, not the section. Keep backgrounds and images full-width if you want, but put a
max-widthon paragraphs. Baymard suggests about70chor34emto stay under 80 characters, adjusted for your font. Achunit is the width of the font’s “0”, so the actual character count varies by typeface. - Count characters on the real layout. Measure a few typical lines of body copy at common desktop widths and aim for roughly 50–75.
- Set body text in
rem, at 16px or above. Consider 18–19px for long-form service and process copy. Rello’s results and GOV.UK’s scale both argue against small body text. - Don’t shrink body text on phones. Larger headings can scale down on small screens, but GOV.UK’s change suggests keeping body text the same size.
- Use a moderate unitless line height, around 1.3–1.6. Rello’s two extremes, which hurt comprehension, correspond to CSS line heights of about 0.96 and 2.16, while the conditions that did well were about 1.2 and 1.68.
- Test the WCAG 1.4.12 overrides. Apply line height 1.5, paragraph spacing 2×, letter spacing 0.12×, and word spacing 0.16×, and check that buttons, cards, and navigation don’t clip or overlap.
- Check landscape phones and tablets. Baymard notes that line length is less of an issue on portrait phones but can come back in landscape.
- Break up long explanations. Baymard recommends mixing blocks of text with bullet lists and organizing descriptions around feature highlights. Short paragraphs and descriptive subheadings do the same job on service pages.
What goes wrong when this step is skipped
- A consultancy’s “Our approach” section runs edge to edge on a large monitor. Each line takes in more than 120 characters, and visitors are more likely to skim the first sentence and move on.
- A mobile type scale reduces body text to 14px so the pricing table fits, and visitors zoom in, lose their place, or leave.
- Cards with fixed heights look tidy in the mockup, then clip their last line when a user increases line spacing.
Practical takeaways for your next website
- Choose line length deliberately. Constrain paragraph width separately from section width, and aim for about 50–75 characters.
- Lean toward larger body text. 16px is a minimum, not a target. Long service copy often reads better at 18–19px.
- Keep body text the same size on mobile. Scale headings down if you need to, but leave paragraphs alone.
- Design for user adjustment. Layouts should allow larger spacing without clipping, as WCAG 1.4.12 requires.
- Hold the numbers lightly. The studies behind them are small, lab-based, and mostly desktop. Use them as defaults, then review real pages, real copy, and real devices.
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