The mathsize global attribute sets the font-size of a MathML element.

Note: Use CSS for styling MathML whenever possible. The mathsize attribute should only be included for applications that are not CSS-aware and will be overridden by the CSS font-size property , if set.


<!-- <length> values -->
<math mathsize="12px">
<math mathsize="0.8em">

<!-- <percentage> values -->
<math mathsize="80%">



A positive <length> value. For most font-relative units (such as em and ex), the font size is relative to the parent element's font size.


A positive <percentage> value, relative to the parent element's font size.


MathML Core
# dfn-mathsize
  • In MathML 3 and earlier versions, keywords small, normal, and big as well as the MathML3-specific syntax for lengths was supported. Since MathML Core, the syntax matches CSS <length-percentage> values.
  • This attribute was designed for MathML applications that are not CSS-aware. Since MathML Core, the use of equivalent CSS is recommended instead.

Browser compatibility

BCD tables only load in the browser

See also