Interlinia

Interlinia refers to the vertical distance between the baselines of successive lines of text, commonly called leading in English typography. It is the space that sits above the text body and below the line above, effectively determining how tightly or loosely lines are stacked. The term originates from traditional metal typesetting, where thin strips of lead were inserted between lines to create the desired spacing.

In practice, interlinia is the sum of the font’s height and the additional space added to separate lines. It is usually expressed in points or as a percentage of the font size. For example, a font set at 12 points with 14 points of leading yields a 2-point interlinia. In body text, typographers often aim for a leading around 120% to 140% of the font size, though the optimal value depends on the typeface, medium, and reading distance. In digital typesetting, line height is controlled by line-height settings in CSS or by leading values in page layout software, and can be specified as an absolute length or as a multiple of the font size.

Appropriate interlinia enhances readability and aesthetics, while too little spacing can cause lines to appear crowded and collide, and too much spacing can disrupt the reading flow. Designers adjust interlinia to accommodate different fonts, sizes, and languages, balancing legibility with visual harmony. Related concepts include line height in digital typography and leading in print, both serving the same fundamental purpose of controlling vertical text density.