Maintain the aspect ratio of a div with CSS

Question

I want to create a div that can change its width/height as the window's width changes.

Are there any CSS3 rules that would allow the height to change according to the width, while maintaining its aspect ratio?

I know I can do this via JavaScript, but I would prefer using only CSS.

Answer 1

This is an improvement on the accepted answer:

• Uses pseudo elements instead of wrapper divs
• The aspect ratio is based on the width of the box instead of its parent
• The box will stretch vertically when the content becomes taller

.box {
  margin-top: 1em;
  margin-bottom: 1em;
  background-color: #CCC;
}

.fixed-ar::before {
  content: "";
  float: left;
  width: 1px;
  margin-left: -1px;
}
.fixed-ar::after {
  content: "";
  display: table;
  clear: both;
}

.fixed-ar-16-9::before {
  padding-top: 56.25%;
}
.fixed-ar-3-2::before {
  padding-top: 66.66%;
}
.fixed-ar-4-3::before {
  padding-top: 75%;
}
.fixed-ar-1-1::before {
  padding-top: 100%;
}

.width-50 {
  display: inline-block;
  width: 50%;
}
.width-20 {
  display: inline-block;
  width: 20%;
}

<div class="box fixed-ar fixed-ar-16-9">16:9 full width</div>
<hr>
<div class="box fixed-ar fixed-ar-16-9 width-50">16:9</div>
<hr>
<div class="box fixed-ar fixed-ar-16-9 width-20">16:9</div>
<div class="box fixed-ar fixed-ar-3-2 width-20">3:2</div>
<div class="box fixed-ar fixed-ar-4-3 width-20">4:3</div>
<div class="box fixed-ar fixed-ar-1-1 width-20">1:1</div>
<hr>
<div class="box fixed-ar fixed-ar-16-9 width-20">16:9</div>
<div class="box fixed-ar fixed-ar-16-9 width-50">16:9</div>

Answer 2

You can use the flux layout (FWD).

https://en.wikipedia.org/wiki/Adaptive_web_design

It will scale and maintain the layout, its a bit complex but allows for a page to resize without pushing the content like (RWD).

It looks like responsive but it is scaling. https://www.youtube.com/watch?v=xRcBMLI4jbg

You can find the CSS scaling formula here:

http://plugnedit.com/pnew/928-2/

Answer 3

Say that you to maintain Width: 100px and Height: 50px (i.e., 2:1) Just do this math:

.pb-2to1 {
  padding-bottom: calc(50 / 100 * 100%); // i.e., 2:1
}

Answer 4

I stumbled upon a smart solution using <svg> and display:grid.

Grid element allows you to occupy the same space with two (or more) elements, without needing to specify which one sets the height. Which means that, out of the box, the taller one sets the ratio.

This means you can use it as is when you know the content will never be tall enough to fill the entire "ratio" and you're simply looking for a way to position the content in this space (i.e. to center it on both directions use display:flex; align-items:center; justify-content:center).
It's pretty much the same as using a transparent <img> with display:block and predetermined ratio, except the <svg> is lighter and considerably easier to modify (to change the ratio responsively, should you need to).

<div class="ratio">
  <svg viewBox="0 0 1 1"></svg>
  <div>
    I'm square
  </div>
</div>

.ratio {
  display: grid;
}
.ratio > * {
  grid-area: 1/1/1/1;
}

All you need to do is change the <svg>s ratio:

• <svg viewBox="0 0 4 3"></svg>
• <svg viewBox="0 0 16 9"></svg>

See it working:

.ratio {
  display: grid;
}
.ratio > * {
  grid-area: 1/1/1/1;
}

/* below code NOT needed for setting the ratio 
 * I just wanted to mark it visually
 * and center contents
 */
.ratio div {
  border: 1px solid red;
  display: flex;
  align-items: center;
  justify-content: center;
}

<div class="ratio">
  <svg viewBox="0 0 7 1"></svg>
  <div>
    Fixed ratio 7:1
  </div>
</div>

---

If you need a solution where the content element is not allowed to set the ratio when it's taller (with overflow hidden or auto), you need to set position:relative on the grid and position:absolute; height:100%; overflow-y: auto; on the content. Example:

.ratio {
  display: grid;
  position: relative;
}
.ratio > * {
  grid-area: 1/1/1/1;
}


.ratio > div {
  height: 100%;
  overflow-y: auto;
  position: absolute;
  
  /* the rest is not needed */
  border: 1px solid red;
  padding: 0 1rem;
}

<div class="ratio">
  <svg viewBox="0 0 7 1"></svg>
  <div>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. A scelerisque purus semper eget. Sem nulla pharetra diam sit amet nisl suscipit adipiscing bibendum. A cras semper auctor neque vitae tempus quam pellentesque nec. Morbi enim nunc faucibus a pellentesque sit amet porttitor. Arcu odio ut sem nulla. Sed viverra ipsum nunc aliquet bibendum enim facilisis gravida neque. Cras tincidunt lobortis feugiat vivamus at augue eget. Laoreet sit amet cursus sit amet. Amet nulla facilisi morbi tempus iaculis urna id volutpat. Leo in vitae turpis massa sed elementum tempus egestas sed. Egestas integer eget aliquet nibh. Dolor sit amet consectetur adipiscing elit.

<p>Ut aliquam purus sit amet. Eget magna fermentum iaculis eu non diam phasellus vestibulum. Diam in arcu cursus euismod quis viverra nibh. Nullam vehicula ipsum a arcu cursus vitae congue. Vel orci porta non pulvinar neque laoreet suspendisse. At tellus at urna condimentum mattis pellentesque. Tristique senectus et netus et malesuada. Vel pretium lectus quam id leo in. Interdum velit euismod in pellentesque. Velit euismod in pellentesque massa placerat duis. Vitae suscipit tellus mauris a diam maecenas sed enim.

<p>Mauris a diam maecenas sed enim ut sem. In hendrerit gravida rutrum quisque. Amet dictum sit amet justo donec enim diam. Diam vulputate ut pharetra sit amet aliquam id. Urna porttitor rhoncus dolor purus non enim praesent. Purus in massa tempor nec feugiat nisl pretium. Sagittis vitae et leo duis ut. Facilisi nullam vehicula ipsum a arcu cursus vitae congue mauris. Volutpat odio facilisis mauris sit amet massa vitae tortor condimentum. Aliquam purus sit amet luctus venenatis lectus magna. Sit amet purus gravida quis blandit turpis. Enim eu turpis egestas pretium aenean. Consequat mauris nunc congue nisi. Nunc sed id semper risus in hendrerit gravida rutrum. Ante metus dictum at tempor. Blandit massa enim nec dui nunc mattis enim ut.
  </div>
</div>

Answer 5

While most answers are very cool, most of them require to have an image already sized correctly... Other solutions only work for a width and do not care of the height available, but sometimes you want to fit the content in a certain height too.

I've tried to couple them together to bring a fully portable and re-sizable solution... The trick is to use to auto scaling of an image but use an inline svg element instead of using a pre-rendered image or any form of second HTTP request...

div.holder{
  background-color:red;
  display:inline-block;
  height:100px;
  width:400px;
}
svg, img{
  background-color:blue;
  display:block;
  height:auto;
  width:auto;
  max-width:100%;
  max-height:100%;
}
.content_sizer{
  position:relative;
  display:inline-block;
  height:100%;
}
.content{
  position:absolute;
  top:0;
  bottom:0;
  left:0;
  right:0;
  background-color:rgba(155,255,0,0.5);
}

<div class="holder">
  <div class="content_sizer">
    <svg width=10000 height=5000 />
    <div class="content">
    </div>
  </div>
</div>

Notice that I have used big values in the width and height attributes of the SVG, as it needs to be bigger than the maximum expected size as it can only shrink. The example makes the div's ratio 10:5

Answer 6

If you want to fit a square inside the viewport on either portrait or landscape view (as big as possible, but nothing sticking outside), switch between using vw/vh on orientation portrait/landscape:

@media (orientation:portrait ) {
  .square {
    width :100vw;
    height:100vw;
  }
} 
@media (orientation:landscape) {
  .square {
    width :100vh;
    height:100vh;
  }
}