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The Science of Typography: How Line Height Affects Readability
Stop squishing your text together. Learn how subtle adjustments to line height and letter spacing can drastically improve your website's scannability.
Utilzy TeamMarch 15, 20265 min read
The Invisible Architecture of Text
When we think about typography, we usually focus on the physical shape of the letters—whether a font is a classic serif like Times New Roman or a modern sans-serif like Inter. However, professional typographers know that the blank space surrounding the letters is just as critical as the letters themselves.
Line height (known in print design as 'leading') is the vertical space between multiple lines of text within a paragraph. When text is packed too tightly, the eye struggles to track back from the end of one line to the beginning of the next, leading to 'doubling' (rereading the same line) and cognitive fatigue. Conversely, if lines are spread too far apart, the paragraph loses cohesion and appears as a disjointed list of sentences.
The Golden Ratio of Line Height
While there is no single universally perfect line height—because optimal spacing relies heavily on the specific font's x-height—there is a generally accepted golden rule for digital design. Body text should typically have a line height of 1.4 to 1.6 times the font size.
For example, if your font size is 16px, your line height should ideally sit between 22px and 26px (or a CSS value of 1.5). This provides enough visual breathing room for the eye to scan horizontally without getting lost. Headings, because they are larger and generally span fewer lines, require much tighter line heights, usually between 1.1 and 1.25.
Responsive Spacing Issues
A major trap in modern web development is static line heights. A 1.6 line height might look gorgeous on a wide desktop monitor where a line spans 80 characters, but on a cramped mobile screen where text breaks every 30 characters, the same ratio can look strangely airy.
The best practice is to utilize responsive typography tools to scale your line height dynamically. Narrower columns of text require slightly tighter line heights, while wider blocks need looser spacing to guide the reader's eye securely across the long horizontal void.
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