readable-measure
The readable-measure skill guides designers and developers in setting optimal text column widths for comfortable reading by maintaining 45 to 75 characters per line across devices. It provides context-specific targets, CSS implementation patterns using the `ch` unit, and responsive strategies ensuring text remains legible on mobile, tablet, and desktop layouts without eye strain.
git clone --depth 1 https://github.com/Owl-Listener/designer-skills /tmp/readable-measure && cp -r /tmp/readable-measure/ui-design/skills/readable-measure ~/.claude/skills/readable-measureSKILL.md
# 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
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