mathsize

Deprecated

Avoid using this feature in new projects. Only MathML Core (a subset of MathML Full) is designed to work with web technologies, such as CSS. This feature may be a candidate for removal from web standards or browsers.

Consider using the following features instead: MathML.

Learn more
See full compatibility

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.

Example

html,
body {
  height: 100%;
}

body {
  display: grid;
  place-items: center;
}

html

<math display="block">
  <msup mathsize="16px">
    <mi>a</mi>
    <mn>2</mn>
  </msup>
  <mo>+</mo>
  <msup mathsize="24px">
    <mi>b</mi>
    <mn>2</mn>
  </msup>
  <mo>=</mo>
  <msup mathsize="32px">
    <mi>c</mi>
    <mn>2</mn>
  </msup>
</math>

Syntax

html

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

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

Values

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

Note: Some browsers may also accept legacy MathML lengths.

Specifications

Specification
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

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This page was last modified on Oct 30, 2025 by MDN contributors.

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