Keep Div Height Relevant to Aspect Ratio

Keep div height relevant to aspect ratio

I did find an answer to this. It adds a little bit of unsemantic markup, but works well.
Can find it here: http://jsfiddle.net/AdQ3P/

The logic is in the padding-bottom. basically this needs to be (img_height / img_width) * 100.

Edit Here's the code, so not dependent on jsfiddle.

<div class="container">
  <div class="hero"></div>
</div>

.container {
  width:100%;
  max-width:500px;
}

.hero {
  width:100%;
  height:0;
  background-size:100%;
  background:url(http://img97.imageshack.us/img97/3410/photo2ue.jpg) no-repeat;
  padding-bottom:75%;
}

Also that was one messy desk i had lol.

Maintain div aspect ratio according to height

You can use an image that has the desired proportions as to help with proportional sizing (images can be scaled proportionally by setting one dimension to some value and other to auto). The image does not have to be visible, but it must occupy space.

.box {

  position: absolute;

  bottom: 0;

  left: 0;

  height: 50%;

}

.size-helper {

  display: block;

  width: auto;

  height: 100%;

}

.inner {

  position: absolute;

  top: 0;

  bottom: 0;

  left: 0;

  right: 0;

  background: rgba(255, 255, 153, .8);

}

<div class="box">

  <img class="size-helper" src="//dummyimage.com/200x100/999/000" width="200" height="100">

  <div class="inner">

    1. box has fluid height<br>

    2. img has 2:1 aspect ratio, 100% height, auto width, static position<br>

    2.1 it thus maintains width = 200% of height<br>

    2.2 it defines the dimensions of the box<br>

    3. inner expands as much as box

  </div>

</div>

Maintain the aspect ratio of a div with CSS

Just create a wrapper <div> with a percentage value for padding-bottom, like this:

.demoWrapper {
  padding: 10px;
  background: white;
  box-sizing: border-box;
  resize: horizontal;
  border: 1px dashed;
  overflow: auto;
  max-width: 100%;
  height: calc(100vh - 16px);
}

div {
  width: 100%;
  padding-bottom: 75%;
  background: gold; /** <-- For the demo **/
}

<div class="demoWrapper">
  <div></div>
</div>

Maintain aspect ratio according to width and height

The aspect-ratio property (2022)

To maintain the aspect ratio of a div according to width and height, you can use the aspect-ratio property (MDN reference).

This allows you to maintain any aspect ratio according to the viewport size or to the size of the parent element.

Maintaining aspect-ratio according to the viewport size (width and height) :

.ar-1-1 {
  aspect-ratio: 1 / 1;
  background: orange;
}

.ar-1-19 {
  aspect-ratio: 16 / 9;
  background: pink;
}

div {
  max-width: 100vw;
  max-height: 100vh;
  margin-bottom: 5vh;
}

/** For the demo **/

body {
  margin: 0;
}

<div class="ar-1-1">Aspect ratio 1:1</div>
<div class="ar-1-19">Aspect ratio 1:19</div>

Maintain aspect ratio of a div according to height

As % padding/margin are calculated according to the width of the contrainer, you can't use the "padding technique" to maitain aspect ratio according to the height.

For a CSS solution, you will have to use vh units :

vh : 1/100th of the height of the viewport.

Source

For browser support see canIuse

---

Example for a 1:1 aspect ratio :

DEMO

CSS

div{
    width: 50vh;
    height: 50vh;
}

Keep aspect ratio of div. while using max-width

You could apply the padding-bottom to its ::before pseudoelement, e.g.

.some-class {
  width: 100%;
  max-width: 520px;
  border: 1px #9bc solid;
}
.some-class::before {
   padding-bottom: 100%;
   content: "";
   display: inline-block;
   vertical-align: top;
}

demo

Doing so the padding is always computed relatively to the actual width of the div and not to the width of its ancestor (e.g. the body element)

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Update (05/2021)

On recent browsers you could start using the new aspect-ratio property, so if the browser supports it you could simply write

.some-class {
  width: 100%;
  max-width: 520px;
  border: 1px #9bc solid;
  aspect-ratio: 1;
}

---

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