Unit Rulebook

Type a unit, or a word from its description.

    ic

    The width of the CJK water ideograph (水) in the current font.

    Safe to useBaseline: widely available

    First version with support, from MDN browser data
    BrowserSince
    Chrome106+
    Chrome Android106+
    Edge106+
    Firefox97+
    Firefox Android97+
    Safari15.4+
    Safari iOS15.4+

    Formula 1ic = advance of 水 (U+6C34) in the element's font (1em if it cannot be measured)

    How it works

    1ic is the advance of the CJK water ideograph 水 (U+6C34) in the element’s font. Chinese, Japanese and Korean text is set on a grid of equal cells, and this one glyph stands in for the cell: inline-size: 20ic holds a line of twenty ideographs in that font, and text-indent: 1ic indents by one.

    The glyph is measured, so the number belongs to the font. In Chromium, a test font whose 水 was 0.9em wide gave 1ic of 0.9em, and one whose 水 was exactly an em gave 1em. The word in the specification is advance measure, the distance a glyph takes along the line.

    A font with no ideographs gives the browser nothing to measure. The specification then assumes one em, and Chromium does so: in IBM Plex Sans, 1ic came out as exactly the font size. On a page that mixes scripts, ic can quietly turn into em for Latin-only fonts.

    The rounding described for ch applies here too: on Linux, Chromium 156 gave 1ic of 14px for an ideograph that advances 14.4px, and macOS gave 14.4px.

    Try it

    Measure the font-relative units

    Pick a font and a size. The page measures 1em, 1ex, 1ch, 1cap and 1lh in that font, here, in your browser.

    UnitMeasuredShare of the font size
    1em
    1ex
    1ch
    1cap
    1lh
    The same as a table
    What each font-relative unit measures
    UnitMeasures
    1emThe font size of the element.
    1exHow tall the letter x is in this font.
    1chThe width of the digit zero in the font.
    1capThe height of a capital letter in the font.
    1lhThe line height of the element.

    What changes it

    Moves with
    • the reader's text size
    • page zoom
    • the font in use
    Stays put under
    • the window size
    • the query container
    • phone toolbars
    • the writing mode

    Reach for it when

    Line lengths and indents counted in ideographs in Chinese, Japanese or Korean text.

    Watch out

    A font without CJK glyphs cannot measure the ideograph, and the unit falls back to 1em. Two different Latin fonts then report the same ic.

    Example ch counts Latin zeros; ic counts ideographs, so the line holds about forty of them.

    Before

    .note {
  max-inline-size: 40ch;
}

    After

    .note {
  max-inline-size: 40ic;
}
    • ricThe width of the ideograph 水, taken from the font set on the root element.
    • chThe width of the zero digit in the current font.
    • QThe quarter-millimeter, a unit taken from Japanese phototypesetting.

    MDNSpecification