How to Fill 100% of Remaining Height

Make a div fill the height of the remaining screen space

2015 update: the flexbox approach

There are two other answers briefly mentioning flexbox; however, that was more than two years ago, and they don't provide any examples. The specification for flexbox has definitely settled now.

Note: Though CSS Flexible Boxes Layout specification is at the Candidate Recommendation stage, not all browsers have implemented it. WebKit implementation must be prefixed with -webkit-; Internet Explorer implements an old version of the spec, prefixed with -ms-; Opera 12.10 implements the latest version of the spec, unprefixed. See the compatibility table on each property for an up-to-date compatibility status.

(taken from https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Flexible_boxes)

All major browsers and IE11+ support Flexbox. For IE 10 or older, you can use the FlexieJS shim.

To check current support you can also see here:
http://caniuse.com/#feat=flexbox

Working example

With flexbox you can easily switch between any of your rows or columns either having fixed dimensions, content-sized dimensions or remaining-space dimensions. In my example I have set the header to snap to its content (as per the OPs question), I've added a footer to show how to add a fixed-height region and then set the content area to fill up the remaining space.

html,body {  height: 100%;  margin: 0;}
.box {  display: flex;  flex-flow: column;  height: 100%;}
.box .row {  border: 1px dotted grey;}
.box .row.header {  flex: 0 1 auto;  /* The above is shorthand for:  flex-grow: 0,  flex-shrink: 1,  flex-basis: auto  */}
.box .row.content {  flex: 1 1 auto;}
.box .row.footer {  flex: 0 1 40px;}

<!-- Obviously, you could use HTML5 tags like `header`, `footer` and `section` -->
<div class="box">  <div class="row header">    <p><b>header</b>      <br />      <br />(sized to content)</p>  </div>  <div class="row content">    <p>      <b>content</b>      (fills remaining space)    </p>  </div>  <div class="row footer">    <p><b>footer</b> (fixed height)</p>  </div></div>

How to fill 100% of remaining height?

You should be able to do this if you add in a div (#header below) to wrap your contents of 1.

If you float #header, the content from #someid will be forced to flow around it.
Next, you set #header's width to 100%. This will make it expand to fill the width of the containing div, #full. This will effectively push all of #someid's content below #header since there is no room to flow around the sides anymore.
Finally, set #someid's height to 100%, this will make it the same height as #full.

JSFiddle

HTML

<div id="full">
    <div id="header">Contents of 1</div>
    <div id="someid">Contents of 2</div>
</div>

CSS

html, body, #full, #someid {
  height: 100%;
}

#header {
  float: left;
  width: 100%;
}

Update

I think it's worth mentioning that flexbox is well supported across modern browsers today. The CSS could be altered have #full become a flex container, and #someid should set it's flex grow to a value greater than 0.

html, body, #full {
  height: 100%;
}

#full {
  display: flex;
  flex-direction: column;
}

#someid {
  flex-grow: 1;
}

Make inner div fill remaining height using flex

I edited @Sfili_81's answer and added these to the *

margin: 0;
padding: 0;

Here's the entire code

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

.home-content {
  display: flex;
  border: 1px solid black;
  height: 100vh;
  flex-flow: column;
}

.container {
  flex: 1;
  display: flex;
  flex-direction: column;
  border: 1px solid red;
}

#listItems {
  border: 3px solid green;
  flex: 1 1 100%;
}

<div class="home-section">
  <div class="home-content">
    <div class="container">
      <form>
        <label for="example">Input</label>
        <input type="text" name="example">
      </form>
      <div id="listItems">

      </div>
    </div>
  </div>
</div>

Put content in 100% remaining height after navbar

Don't set the #map position to absolute as it's not needed for this.

All you have to do is set the height of #map to calc(100vh - 80px).

#map { 
  width: 100%;
  height: calc(100vh - 80px);
  background: red;
 }

.nav {
  background: hotpink;
  height: 80px;
}

Which will take the height of the page and subtract the height of the nav.

How can an html element fill out 100% of the remaining screen height, using css only?

The trick to this is specifying 100% height on the html and body elements.
Some browsers look to the parent elements (html, body) to calculate the height.

<html>
    <body>
        <div id="Header">
        </div>
        <div id="Content">
        </div>
    </body>
</html>

html, body
{
    height: 100%;
}
#Header
{
    width: 960px;
    height: 150px;
}
#Content
{
    height: 100%;
    width: 960px;
}

CSS Div fill remaining height

Give the container:

display:flex;
flex-direction:column;

and for the element:

flex:1;

The demo:
https://jsfiddle.net/ugjfwbg4/1/

body {  background-color: red;  height: 100%;}
.wrap {  height: 100vh;  width: 100%;  padding: 20px;  background-color: yellow;  display:flex;  flex-direction:column;}
.top {  width: 100%;  height: 50px;  background-color: blue;}
.mid {  width: 100%;  background-color: green;  flex:1;  display:flex;  flex-direction:column;}
.left{  flex:1;  width: 50%;  background-color: red;}
.bottom {  width: 100%;  height: 50px;  background-color: blue;}

<div class="wrap">  <div class="top"></div>
  <div class="mid">        <div class="left">left</div>  </div>
  <div class="bottom"></div></div>

How to make div occupy remaining height?

Use absolute positioning:

#div1{    width: 100%;    height: 50px;    background-color:red;/*Development Only*/}#div2{    width: 100%;    position: absolute;    top: 50px;    bottom: 0;    background-color:blue;/*Development Only*/}

<div id="div1"></div><div id="div2"></div>

Div to fill 100% height of available space

Here's a solution using height:calc(); https://jsfiddle.net/DTcHh/16058/

It was kind of hard to set due to your body padding but it works.

.bottom-row {
  height:calc(100vh - 335px);
}

.col-xs-4 {
  height:100%;
  background-color: red;
  color: white;
}