In type design, height refers to vertical measurements used as guidelines for different categories of glyphs (such as uppercases, lowercases, small caps, etc.). These are measured from the baseline and help ensure visual consistency across the typeface.

LCG (LATIN, CYRILLIC, GREEK)

LCG scripts typically use the following height guidelines for their lowercases, uppercases, and small caps:
• x-height: height of short lowercases;
• ascender height: height of the extension of lowercase letters that rise above the x-height;
• descender height: height of the extension of lowercase letters that fall below the baseline;
• cap height: height of uppercase letters;
• small case height: heigh of the small cases;
• sometimes also specific figure heights too (for old style or proportional figures, and more).

CJK (CHINESE, JAPANESE, KOREAN)

Characters of CJK scripts are commonly designed to fit within a common em-square (same width and/or height) for all characters within the same typeface. Designers often define:
• ideographic em height: total vertical space for a character;
• baseline offset: vertical alignment for mixed-script texts.

ARABIC SCRIPTS

Arabic scripts have various types of heights measurements depending on the style involved, including some that don’t follow the same rule as Latin script, where the “horizontal” baseline may not be exactly the same word to word when the letters are typed into texts. But in general, we can list down the following:
• baseline: anchors the “horizontal” alignment;
• median line: main body height;
• ascender and descender lines: based on the tallest and lowest glyph strokes;
• mark height: guides the placement of diacritics.

INDIC SCRIPTS

The following are the most common height measurements for Indic scripts (which encompasses a large number of different scripts!):
• shirorekha (headline): the horizontal bar on top of many letters;
• base height: where the main glyph body sits;
• matra height: position for vowel signs and marks above or below the base glyph.

Note: These design heights relate to glyphs’ outlines, and are not to be confused with vertical metrics, which define the overall line spacing in a font.

FONT ENGINEERING ADVICE

The x-height and the cap-height are important values that can be found in the OS/2 table of the font file.