Divide Width of Element Between Child Divs With CSS

You can use display:table-cell on your inner divs to do this. For the browser to make the inner divs behave like table cells, it also needs two layers of containing elements: one to acts as the table, and another to act as the table-row.

For a structure like this:

   <div class="outer">
       <div class="middle">
          <div class="inner">Item 1</div> 
          <div class="inner">Item 2</div> 
          <div class="inner">Item 3</div> 
          <div class="inner">Item 4</div> 
       </div>
   </div>

Use this CSS:

div.outer {display:table;}
div.middle {display:table-row;}
div.inner {display:table-cell;}

A nice structure to use is a UL wrapped in a DIV: the DIV acts as a table, the UL as a row, and the LI's as table-cells.

This technique is not well supported in older browsers - for anything older than IE8, you're out of luck entirely.

Let me know if you need more sample code than that!

You can utilize css3 benefits here. I was also facing this issue now i have fixed that using below example code

.parent-container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-flow: row wrap;
  justify-content: space-around;
  -webkit-justify-content: space-around;
  flex-wrap: nowrap;
  -webkit-flex-wrap: nowrap;
}
.child-item {
  margin: 5px;
  text-align: center;
  padding: 10px;
  background-color: red;
  color: #fff;
}

<ul class="parent-container">
  <li class="child-item">1</li>
  <li class="child-item">2</li>
  <li class="child-item">3</li>
  <li class="child-item">4</li>
  <li class="child-item">5</li>
  <li class="child-item">6</li>
  <li class="child-item">7</li>
</ul>

Thanks & Regards, Lingeshram

The accepted answer missed an important CSS property which is necessary to work:

table-layout: fixed;

This is the correct answer:

HTML:

<div class="outer">
    <div class="middle">
        <div class="inner">Item 1</div> 
            <div class="inner">Item 2</div> 
            <div class="inner">Item 3</div> 
            <div class="inner">Item 4</div> 
        </div>
    </div>
</div>

CSS:

div.outer {display:table; table-layout: fixed;}
div.middle {display:table-row;}
div.inner {display:table-cell;}

I'd like to expound on @lingeshram's answer. Flexboxes have come so far that I think it's really the way to do it now. If you have to support old browsers, be sure to check caniuse first.

.container {
  display: flex; /* or inline-flex */
}

.col {
  flex-grow: 1;
  border: 1px solid #000;
}

.col2x {
  flex-grow: 2;
  border: 1px solid #000;
}

Evenly split three children
<div class='container'>
  <span class='col'>Inner 1</span>
  <span class='col'>Inner 2</span>
  <span class='col'>Inner 3</span>
</div>

<br>
Evenly split two children
<div class='container'>
  <span class='col'>Inner 1</span>
  <span class='col'>Inner 2</span>
</div>

<br>
Split three children, but the middle is twice the size of the others
<div class='container'>
  <span class='col'>Inner 1</span>
  <span class='col2x'>Inner 2</span>
  <span class='col'>Inner 3</span>
</div>

Here is a pretty good guide to the different ways you can use flexbox.