GeezerVison is showing developer.mozilla.org — <percentage> CSS type - CSS | MDN
<percentage> CSS type
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The <percentage> CSS data type represents a percentage value. It is often used to define a size as relative to an element's parent object. Numerous properties can use percentages, such as width, height, margin, padding, and font-size.
Note:
Only calculated values can be inherited. Thus, even if a percentage value is used on the parent property, a real value (such as a width in pixels for a <length> value) will be accessible on the inherited property, not the percentage value.
The <percentage> data type consists of a <number> followed by the percentage sign (%). Optionally, it may be preceded by a single + or - sign, although negative values are not valid for all properties. As with all CSS dimensions, there is no space between the symbol and the number.
When animated, values of the <percentage> data type are interpolated as real, floating-point numbers. The speed of the interpolation is determined by the easing function associated with the animation.
html
<div class="container">
<div class="box1">Width: 50%, Left margin: 20%</div>
<div class="box2">Width: 30%, Left margin: 60%</div>
</div>
css
.container {
background-color: navy;
}
.box1 {
width: 50%;
margin-left: 20%;
background-color: chartreuse;
}
.box2 {
width: 30%;
margin-left: 60%;
background-color: pink;
}
html
<div class="container">
<p>Full-size text (18px)</p>
<p><span class="half">50% (9px)</span></p>
<p><span class="double">200% (36px)</span></p>
</div>
css
.container {
font-size: 18px;
}
.half {
font-size: 50%;
}
.double {
font-size: 200%;
}