fontSizeAdjust property

[This documentation is preliminary and is subject to change.]

Sets or retrieves a value that specifies an aspect value for an element that will effectively preserve the x-height of the first choice font, whether it is substituted or not.

Scalable Vector Graphics: Text, Section 10.10Internet Explorer 9


Integer value = object.put_fontSizeAdjust(Variant v);Integer value = object.get_fontSizeAdjust(Variant* sShadow);

Property values


none (none)

Default. Indicates the font's x-height should not be preserved.

number (number)

Specifies the aspect value. For the adjusted font size calculation, see Remarks.

inherit (inherit)

Indicates that the property takes the same computed value as the property for the element's parent.

String format

none | number | inherit

CSS information

Applies To All elements
Media visual
Inherited 1
Initial Value

Standards information


For any given font size, the apparent size and legibility of text varies across fonts. For scripts such as Latin or Cyrillic that distinguish between uppercase and lowercase letters, the relative height of lowercase letters compared to their uppercase counterparts is a determining factor of legibility. This is commonly referred to as the aspect value. Precisely defined, it is equal to the x-height of a font (the height of a font's lowercase 'x' character) divided by the font size.

In situations where font fallback occurs, fallback fonts cannot share the same aspect ratio as the desired font family and thus appear less legible. Font fallback occurs when the specified font is not available and the client uses a fallback font, or a replacement font. The font-size-adjust property is a way to preserve the legibility of text when font fallback occurs. It does this by adjusting the font size so that the x-height is the same regardless of the font that is used.

The following calculation uses the number value to calculate the adjusted font size: c = ( a / a' ) s

In this equation, s is the font-size value, a is the number value of the font-size-adjust property, a' is the aspect value of the actual font, and c is the adjusted font size to use.


Minimum supported client

Windows Vista with SP1, Windows 7

Minimum supported server

Windows Server 2008 R2







See also




Build date: 1/23/2012