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The CSS Font-Size Property

Reading time 1 min
Published Aug 10, 2017
Updated Oct 10, 2019

Defining CSS font sizes

The CSS font-size property allows you to set the default font size in HTML documents or elements:

Example
h1{
  font-size: 250%;
}   
h2{
  font-size: 200%;
}   
p{  
  font-size: 100%;
}

The default value is medium, which equals to 16 pixels. Descendants of the element with a CSS font size defined will inherit it unless they have their font size defined individually.

Writing font-size: CSS syntax

To set a CSS font size, follow the syntax example below:

font-size: value;

All the available property values will be defined in the following section.

Property values

Value Definition
Keywords Define the CSS font size as xx-small, x-small, small, medium, large, x-large or xx-large
Numeric values Define the CSS font size in absolute values (e.g., pixels or millimeters)
Percentages Define the CSS font size in relation to the font size of the parent container in percentages
Relative values Define the CSS font size as larger or smaller in relation to the font size of the parent container

Browser support

Browser image
Chrome
1+
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Edge
12+
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Firefox
1+
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IE
5.5+
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Opera
7+
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Safari
1+

Mobile browser support

Browser image
Chrome
18+
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Firefox
4+
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Opera
10.1+
Browser image
Safari
1+