<absolute-size> = xx-small | x-small | small | medium | large | x-large | xx-large | xxx-large

The <absolute-size> data type is defined using a keyword value chosen from the list below.

xx-small

An absolute size 60% the size of medium. Mapped to the deprecated size="1".

x-small

An absolute size 75% the size of medium.

small

An absolute size 89% the size of medium. Mapped to the deprecated size="2".

medium

A user's preferred font size. This value is used as the reference middle value. Mapped to size="3".

large

An absolute size 20% larger than medium. Mapped to the deprecated size="4".

x-large

An absolute size 50% larger than medium. Mapped to the deprecated size="5".

xx-large

An absolute size twice the size of medium. Mapped to the deprecated size="6".

xxx-large

An absolute size three times the size of medium. Mapped to the deprecated size="7".

Each <absolute-size> keyword value is sized relative to the medium size and the individual device's characteristics, such as device resolution. User agents maintain a table of font sizes for each font, with the <absolute-size> keywords being the index.

In CSS1 (1996), the scaling factor between adjacent keyword value indexes was 1.5, which was too large. In CSS2 (1998), the scaling factor between adjacent keyword value indexes was 1.2, which created issues for the small values. As a single fixed ratio between adjacent absolute-size keywords was found to be problematic, there is no longer a fixed ratio recommendation. The only recommendation to preserve readability is that the smallest font size should not be less than 9px.

For each <absolute-size> keyword value, the following table lists the scaling factor, mapping to <h1> to <h6> headings, and mapping to the deprecated HTML size attribute.

The size attribute to set a font's size in HTML is deprecated. The attribute value was either an integer between 1 and 7 or a relative value. Relative values were an integer preceded by + or - to increase or decrease the font size, respectively. A value of +1 meant increasing the size by one and -2 meant decreasing the size by two, with the computed value clamped at a minimum of 1 and a maximum computed value of 7.

<ul>
  <li class="xx-small">font-size: xx-small;</li>
  <li class="x-small">font-size: x-small;</li>
  <li class="small">font-size: small;</li>
  <li class="medium">font-size: medium;</li>
  <li class="large">font-size: large;</li>
  <li class="x-large">font-size: x-large;</li>
  <li class="xx-large">font-size: xx-large;</li>
  <li class="xxx-large">font-size: xxx-large;</li>
</ul>

li {
  margin-bottom: 0.3em;
}
.xx-small {
  font-size: xx-small;
}
.x-small {
  font-size: x-small;
}
.small {
  font-size: small;
}
.medium {
  font-size: medium;
}
.large {
  font-size: large;
}
.x-large {
  font-size: x-large;
}
.xx-large {
  font-size: xx-large;
}
.xxx-large {
  font-size: xxx-large;
}

Result

• CSS <relative-size> data type
• CSS font and font-size properties
• CSS fonts module