Responsively change div size keeping aspect ratio
HtmlCssResponsive DesignHtml Problem Overview
When I give an image a percent width or height only it will grow/shrink keeping its aspect ratio, but if I want the same effect with another element, is it possible at all to tie the width and the height together using percentage?
Html Solutions
Solution 1 - Html
You can do this using pure CSS; no JavaScript needed. This utilizes the (somewhat counterintuitive) fact that padding-top percentages are relative to the containing block's width. Here's an example:
<div class="wrapper">
<div class="main">
This is your div with the specified aspect ratio.
</div>
</div>
.wrapper {
width: 50%;
/* whatever width you want */
display: inline-block;
position: relative;
}
.wrapper:after {
padding-top: 56.25%;
/* 16:9 ratio */
display: block;
content: '';
}
.main {
position: absolute;
top: 0;
bottom: 0;
right: 0;
left: 0;
/* fill parent */
background-color: deepskyblue;
/* let's see it! */
color: white;
}
Solution 2 - Html
Bumming off Chris's idea, another option is to use pseudo elements so you don't need to use an absolutely positioned internal element.
<style>
.square {
/* width within the parent.
can be any percentage. */
width: 100%;
}
.square:before {
content: "";
float: left;
/* essentially the aspect ratio. 100% means the
div will remain 100% as tall as it is wide, or
square in other words. */
padding-bottom: 100%;
}
/* this is a clearfix. you can use whatever
clearfix you usually use, add
overflow:hidden to the parent element,
or simply float the parent container. */
.square:after {
content: "";
display: table;
clear: both;
}
</style>
<div class="square">
<h1>Square</h1>
<p>This div will maintain its aspect ratio.</p>
</div>
I've put together a demo here: http://codepen.io/tcmulder/pen/iqnDr
EDIT:
Now, bumming off of Isaac's idea, it's easier in modern browsers to simply use vw units to force aspect ratio (although I wouldn't also use vh as he does or the aspect ratio will change based on window height).
So, this simplifies things:
<style>
.square {
/* width within the parent (could use vw instead of course) */
width: 50%;
/* set aspect ratio */
height: 50vw;
}
</style>
<div class="square">
<h1>Square</h1>
<p>This div will maintain its aspect ratio.</p>
</div>
I've put together a modified demo here: https://codepen.io/tcmulder/pen/MdojRG?editors=1100
You could also set max-height, max-width, and/or min-height, min-width if you don't want it to grow ridiculously big or small, since it's based on the browser's width now and not the container and will grow/shrink indefinitely.
Note you can also scale the content inside the element if you set the font size to a vw measurement and all the innards to em measurements, and here's a demo for that: https://codepen.io/tcmulder/pen/VBJqLV?editors=1100
Solution 3 - Html
<style>
#aspectRatio
{
position:fixed;
left:0px;
top:0px;
width:60vw;
height:40vw;
border:1px solid;
font-size:10vw;
}
</style>
<body>
<div id="aspectRatio">Aspect Ratio?</div>
</body>
The key thing to note here is vw = viewport width, and vh = viewport height
Solution 4 - Html
That's my solution
<div class="main" style="width: 100%;">
<div class="container">
<div class="sizing"></div>
<div class="content"></div>
</div>
</div>
.main {
width: 100%;
}
.container {
width: 30%;
float: right;
position: relative;
}
.sizing {
width: 100%;
padding-bottom: 50%;
visibility: hidden;
}
.content {
width: 100%;
height: 100%;
background-color: red;
position: absolute;
margin-top: -50%;
}
Solution 5 - Html
(function( $ ) {
$.fn.keepRatio = function(which) {
var $this = $(this);
var w = $this.width();
var h = $this.height();
var ratio = w/h;
$(window).resize(function() {
switch(which) {
case 'width':
var nh = $this.width() / ratio;
$this.css('height', nh + 'px');
break;
case 'height':
var nw = $this.height() * ratio;
$this.css('width', nw + 'px');
break;
}
});
}
})( jQuery );
$(document).ready(function(){
$('#foo').keepRatio('width');
});
Working example: http://jsfiddle.net/QtftX/1/