Line Length Tester — Optimal Measure Calculator
Resize the preview and measure characters per line to stay within the 45–75 character rule for comfortable reading. Test paragraph width across desktop, tablet, and mobile viewports.
Line Length Tester
Container width: 530px
~63 characters per line
Typography is the craft of endowing human language with a durable visual form. Good measure — the width of a line of text — is essential for comfortable reading.
This measure falls within the optimal 45–75 character range for body text.
What this line length tester — optimal measure calculator does
This line length tester helps you find the optimal measure for readable paragraphs across desktop, tablet, and mobile viewports. Stay within the 45–75 character rule for comfortable sustained reading.
How to use it
Resize the preview container or enter your target viewport width.
Type or paste sample paragraph text to test realistic content.
Aim for 45–75 characters per line for body copy; narrower on mobile is acceptable.
Adjust container width or font size until measure falls in the readable range.
Read the Measure & Readability chapter for context on line height and font size.
Frequently asked questions
What is the ideal line length for web text?
Aim for 45–75 characters per line (roughly 20–35em depending on font). Desktop editorial content often targets 60–75 characters; mobile body text can be 45–60 characters.
How does line length affect readability?
Too-wide lines tire the eye returning to the next line, causing line regressions. Too-narrow lines break too often and disrupt reading rhythm. Correct measure pairs with appropriate line height (1.5–1.7 for body).
What line height should I use with optimal line length?
Use line height between 1.5 and 1.7 for body text at 16–18px. Wider line length can tolerate slightly tighter leading; narrow columns often need more line height.
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