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Optimal Line Length Calculator
Calculate the ideal max-width for readable body text at any font size. Based on the 45 to 75 characters per line rule and outputs values in px, rem, and ch.
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The 45–75 character rule is the gold standard for body text readability.
When would you use this?
Typography research consistently points to the same finding: lines between 45 and 75 characters are the sweet spot for comfortable reading. Too short and the eye jumps lines too frequently; too long and the reader loses their place returning to the start of the next line. This calculator takes your font size and target character count, and outputs a suggested max-width in px, rem, and the useful ch unit (which is literally "one character wide").