BaselineThe invisible line where all characters sit.

Definition: In typography, the baseline is the imaginary line upon which a line of text rests. In most typefaces, the descenders on characters such as g or p extend down below the baseline while curved letters such as c or o extend ever-so-slightly below the baseline. The baseline is the point from which other elements of type are measured including x-height and leading. The baseline is also significant in the alignment of drop caps and other page elements.

In typography and penmanship, the baseline is the line upon which most letters “sit” and below which descenders extend.
In the example to the right, the letter ‘p’ has a descender; the other letters sit on the (red) baseline.
Most, though not all, typefaces are similar in the following ways as regards the baseline:

  • capital letters sit on the baseline. The most common exceptions are the J and Q.
  • Lining figures (see Arabic numerals) sit on the baseline.
  • The following text figures have descenders: 3 4 5 7 9.
  • The following lowercase letters have descenders: g j p q y.
  • Glyphs with rounded lower extents (0 3 5 6 8 c C G J o O Q U) dip very slightly below the baseline (“overshoot”) to create the optical illusion that they sit on the baseline. Peter Karow’s Digital Typefaces suggests that typical overshoot is about 1.5%.

The vertical distance of the base lines of consecutive lines in a paragraph is also known as line height or leading, although the latter can also refer to the baseline distance minus the font size.