Height equal to dynamic width (CSS fluid layout) [

Question

This question already has an answer here:

• Maintain the aspect ratio of a div with CSS 21 answers

Is it possible to set same height as width (ratio 1:1)?

Example

+----------+
| body     |
| 1:3      |
|          |
| +------+ |
| | div  | |
| | 1:1  | |
| +------+ |
|          |
|          |
|          |
|          |
|          |
+----------+

CSS

div {
  width: 80%;
  height: same-as-width
}

Answer 1

Simple and neet : use vw units for a responsive height/width according to the viewport width.

vw : 1/100th of the width of the viewport. (Source MDN)

DEMO

HTML:

<div></div>

CSS for a 1:1 aspect ratio:

div{
    width:80vw;
    height:80vw; /* same as width */
}

---

Table to calculate height according to the desired aspect ratio and width of element.

   aspect ratio  |  multiply width by
    -----------------------------------
         1:1      |         1
         1:3      |         3
         4:3      |        0.75
        16:9      |       0.5625

---

This technique allows you to :

• insert any content inside the element without using position:absolute;
• no unecessary HTML markup (only one element)
• adapt the elements aspect ratio according to the height of the viewport using vh units
• you can make a responsive square or other aspect ratio that alway fits in viewport according to the height and width of the viewport (see this answer : Responsive square according to width and height of viewport or this demo)

These units are supported by IE9+ see canIuse for more info

Answer 2

It is possible without any Javascript :)

This article describes it perfectly - http://www.mademyday.de/css-height-equals-width-with-pure-css.html

The HTML:

<div class='box'>
    <div class='content'>Aspect ratio of 1:1</div>
</div> 

The CSS:

.box {
    position: relative;
    width:    50%; /* desired width */
}

.box:before {
    content:     "";
    display:     block;
    padding-top: 100%; /* initial ratio of 1:1*/
}

.content {
    position: absolute;
    top:      0;
    left:     0;
    bottom:   0;
    right:    0;
}

/* Other ratios - just apply the desired class to the "box" element */
.ratio2_1:before{
    padding-top: 50%;
}
.ratio1_2:before{
    padding-top: 200%;
}
.ratio4_3:before{
    padding-top: 75%;
}
.ratio16_9:before{
    padding-top: 56.25%;
}

Answer 3

Expanding upon the padding top/bottom technique, it is possible to use a pseudo element to set the height of the element. Use float and negative margins to remove the pseudo element from the flow and view.

This allows you to place content inside the box without using an extra div and/or CSS positioning.

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


/* proportions */

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


/* demo */

.fixed-ar {
  margin: 1em 0;
  max-width: 400px;
  background: #EEE url(https://lorempixel.com/800/450/food/5/) center no-repeat;
  background-size: contain;
}

<div class="fixed-ar fixed-ar-1-1">1:1 Aspect Ratio</div>
<div class="fixed-ar fixed-ar-4-3">4:3 Aspect Ratio</div>
<div class="fixed-ar fixed-ar-16-9">16:9 Aspect Ratio</div>

Answer 4

width: 80vmin; height: 80vmin;

CSS does 80% of the smallest view, height or width

http://caniuse.com/#feat=viewport-units

Answer 5

really this belongs as a comment to Nathan's answer, but I'm not allowed to do that yet...
I wanted to maintain the aspect ratio, even if there is too much stuff to fit in the box. His example expands the height, changing the aspect ratio. I found adding

overflow: hidden;
overflow-x: auto;
overflow-y: auto;

to the .element helped. See http://jsfiddle.net/B8FU8/3111/

Answer 6

Extremely simple method jsfiddle

HTML

<div id="container">
    <div id="element">
        some text
    </div>
</div>

CSS

#container {
    width: 50%; /* desired width */
}

#element {
    height: 0;
    padding-bottom: 100%;
}