Maintain Aspect Ratio of a Div According to Height

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 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;
}

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 of a div with dynamic height

Here is one other solution:

We can make an inner div inside the main .square div inherits its parent height.

Then, if we rotate that inner div, its height now becomes its width. So all we've got to do at this point, is to hide the overflow from the parent div, and apply some translation so it ends at the correct position.

#container {

  width: 400px;

  padding: 20px;

  border: solid 1px black;

  position: relative;

}

.square {

  position: absolute;

  top: 0;

  right: 0;

  bottom: 0;

  overflow: hidden;

  pointer-events: none;

}

.square>div {

  background-color: red;

  transform: rotate(-90deg) translate(100%, 0%);

  width: 100vw;

  height: 100%;

  transform-origin: 100% 100%;

}

<div id="container">

  <div class="content">

    <textarea> I'm a dynamic content</textarea>

  </div>

  <div class="square">

    <div></div>

  </div>

</div>

Maintain aspect ratio of div but fill screen width and height in CSS?

There is now a new CSS property specified to address this: object-fit.

https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit

The feature is widely supported by now (http://caniuse.com/#feat=object-fit).

Div that fits into parent and maintains an aspect ratio

Ok, it looks like it can't be solved by CSS only. If anyone interested, I've put together a React component that does the job (Tests and better README soon, when I have time).

It wraps its children into a div and uses JavaScript to compute the width and height of that div in order to accommodate the available space while maintains the given aspect ratio. It basically stretches the wrapper until one of the sides reaches its maximum.

BREAKING UPDATE a CSS only solution has been found!

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)

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;
}