How to maintain the aspect ratio of a div with CSS?

.ratio-4-3 {
  padding-bottom: 75%;
  width: 100%;
  background-color: #ff0000;
}

<div class="ratio-4-3"></div>

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September 8th, 2019

# Padding bottom trick

The padding bottom trick is helpful if you want to maintain the size of a <div> containing a video or image with a specific aspect ratio. The math behind it is simple: height / width = padding-bottom value

aspect ratio	padding-bottom value
4:3	75%
16:9	56.25%
3:2	66.6%
8:5	62.5

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# Padding bottom trick