Set line length and measure for comfortable reading across type sizes and breakpoints. Use when tuning body text. Covers measure only — for the full size and weight scale, use `typography-scale`.
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Use readable-measure to recommend responsive body-text column widths for [page or layout] across mobile, tablet, and desktop.
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[page or layout]
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SKILL.md
name: readable-measuredescription: Set line length and measure for comfortable reading across type sizes and breakpoints. Use when tuning body text. Covers measure only — for the full size and weight scale, use `typography-scale`.
Readable Measure
You are an expert in typographic measure and its effect on reading comfort and comprehension.
What You Do
You apply the principle of readable measure to ensure text columns are sized for comfortable, uninterrupted reading across devices and type scales.
The Principle
Measure is the length of a line of text. The optimal range is 45–75 characters per line (including spaces), with 66 characters often cited as the ideal.
Below 45 characters: too short — the eye jumps lines too frequently, disrupting rhythm
Above 75 characters: too long — the eye loses its place returning to the start of the next line
45–75 is the target zone for body copy; tighter ranges (50–60) suit sustained reading like articles or docs
Measuring in Practice
Use the ch CSS unit (width of the 0 glyph) as a rough proxy: max-width: 65ch
Count actual characters in a representative paragraph to validate — ch is approximate
Adjust for typeface: wide faces (Georgia) need narrower columns; condensed faces allow slightly wider
Display type and short UI strings are exempt — this applies to body copy and reading contexts
Responsive Behavior
Single-column mobile: full width is usually fine at 16px+ (rarely exceeds 70 chars on small screens)
Tablet and desktop: constrain column width explicitly; don't let text stretch to container edge
Multi-column layouts: each column should independently satisfy the 45–75 rule
By Context
Context
Target
Long-form articles, docs
55–70 characters
UI body copy, descriptions
45–65 characters
Captions, helper text
40–60 characters
Pull quotes, callouts
30–45 characters
Best Practices
Set max-width on text containers, not just font size
Increase line-height slightly as column width grows (wider measure needs more leading)
Test with real content — synthetic lorem obscures measure problems
Revisit measure whenever typeface or type size changes