fontsize

Font size is a measure of the height of characters in a typeface and a key factor in readability and visual hierarchy. In both digital and print typography, it helps determine how text occupies space and how emphasis is conveyed across a page or screen.

Common units fall into absolute and relative categories. Absolute units include points (pt) and physical measures such as inches (in) or millimeters (mm); these map to physical size but can vary with printing conditions. Relative units adapt to context: ems (em) scale with the font size of the element, rems (rem) scale with the root element’s size, percentages (%) follow the parent context, and viewport units (vw, vh) scale with the display size. Pixels (px) are CSS pixels in web design, offering a stable reference but still influenced by device pixel ratio. In practice, a mix is used depending on goals for printing accuracy or responsive behavior.

In web development, the font-size property controls size and accepts units, keywords, or functions. Em and rem are popular for creating scalable typography; clamp(), min/max(), and media queries enable responsive sizing. Using relative units supports user zoom and accessibility, while fixed sizes can simplify precise layouts but may hinder readability at small scales.

Best practices emphasize a readable typographic scale, accessible contrast, and a clear hierarchy between body text, headings, and captions. For print, font sizes are often specified in points and tied to typographic metrics, where precise measurement and physical legibility are paramount.