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Why Does Percentage-Based Vertical Padding Fail, and How Can I Use Percentage Heights for Vertical Alignment in CSS?
Why Does Percentage-Based Vertical Padding Fail, and How Can I Use Percentage Heights for Vertical Alignment in CSS?
Dec 11, 2024 pm 08:17 PM
How to Control Padding and Margin Using Percentage of Parent Container Height
In CSS, controlling vertical alignment can be achieved using the padding-top property. However, setting this property as a percentage of the parent container's width instead of height can lead to undesirable behavior.
Original Attempt:
.base {
background-color: green;
width: 200px;
height: 200px;
overflow: auto;
position: relative;
}
.vert-align {
padding-top: 50%;
height: 50%;
}
Unexpected Behavior:
When changing the width of the .base container, the vertical alignment snapped, even though padding-top was set as a percentage. This is because vertical padding and margin are calculated as a percentage of the parent container's width.
Solution:
Instead of using padding-top, use the top property to control vertical alignment. top is calculated as a percentage of the parent container's height.
.base {
background-color: green;
width: 200px;
height: 200px;
overflow: auto;
position: relative;
}
.vert-align {
position: absolute;
top: 50%;
}
This nested div structure places a child div inside the parent container and aligns it vertically:
<div class="base">
<div class="vert-align">
Content Here
</div>
</div>
By using top instead of padding-top, the child div is positioned 50% down from the top of its parent container, regardless of its width. This ensures vertical alignment even when the parent's width changes.
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