CSS Font Size
CSS Font Size
The CSS font-size property
is used to specify the size of the text/font.
Being able to manage the text size is very important in web design.
However, you should not use font size adjustments to make paragraphs look like headings, or headings look like paragraphs. Always use the proper HTML tags, like <h1> - <h6> for headings and <p> for paragraphs.
The font-size can be set to an absolute size or to a relative size.
Absolute sizes:
px: Pixels offers fixed and precise control over the font size.xx-small,x-small,small,medium,large,x-large,xx-large. These keywords has a predefined set of sizes in browsers.
Relative sizes:
em: This unit is relative to the font size of the parent element.rem: This unit is relative to the font size of the root HTML element.%: This unit is relative to the font size of the parent elementsmallerandlarger: These units adjust the font size relative to the parent element.
How to Pick the Right Unit?
- For fixed and precise control,
pxcan be used. - With
px, the web page will not scale well on different screen sizes or with user preferences. - Absolute size can be useful when the physical size of the output is known.
- For scalable web designs, use
emorrem; they allow users to adjust text size in their browser settings. - Percentage (
%) can be useful for adjusting font sizes based on parent elements.
Set Font Size With Pixels
Setting the text size with pixels (px) gives
you full control over the text size.
If you use pixels, the web page may not scale very well on different screen sizes and the users cannot adjust the text size in their browser settings. However, the users can still use the zoom tool to resize the entire page.
Example
Set font sizes with px:
h1 {
font-size: 40px;
}
h2 {
font-size: 30px;
}
p {
font-size: 16px;
}
Try it Yourself »
Set Font Size With Em
The em unit is relative to the font size of
the parent element. So, if the parent element has a font size of 16px, then 2.5em
would result in 40px.
In the following example, the text size in
em is the same as the previous example
in pixels. However, the
em unit allows the user to adjust the text size
in the browser settings.
Example
Set font sizes with em:
body {
font-size: 16px; /* Base font size */
}
h1 {
font-size: 2.5em; /* 2.5 * 16 = 40px */
}
h2 {
font-size: 1.875em; /* 1.875 * 16 = 30px */
}
p {
font-size: 1em; /* 1 * 16 = 16px */
}
Try it Yourself »
Set Font Size With Rem
The rem unit is relative to the font size of
the root HTML element (<html>).
Unlike em, which is relative to the font-size of its parent element, rem
always refers to the font-size of the <html> element, regardless of its position
in the document tree. This makes rem very useful for creating scalable and responsive
designs. By changing the font-size of the <html> element, all elements sized
with rem units will scale proportionally throughout the entire page.
The default font-size of the <html> element in most browsers, is 16px. So, by default, 1rem equals 16px unless explicitly overridden in the CSS.
Example
Set font sizes with rem:
html {
font-size: 16px; /* Set the root font size */
}
h1 {
font-size: 2.5rem; /* 2.5 * 16 = 40px */
}
h2 {
font-size: 1.875rem; /* 1.875 * 16 = 30px */
}
p {
font-size: 1rem; /* 1 * 16 = 16px */
}
Try it Yourself »
The vw Unit
The font size can also be set with the vw unit, which means the "viewport width".
The vw unit is a relative unit that
represents a percentage of the width of the viewport.
1vw = 1% of the current width of the browser's viewport. So, if the viewport is 500px wide, 1vw is 5px.
This way the text size will follow the size of the browser window:
Hello World
Resize the browser window to see how the font size scales.
