Fixed + Dynamic Heights in CSS

11 Feb 2014

Your web project has a fixed-height (let's say 6px) header - and your content should automatically fill the remaining height. Solutions like flexbox are too new and don't have support across current browsers, namely IE.

Percentage-based height values won't work because one or more of the page elements needs a fixed height. There is no "percent remaining" value in CSS unless you're using percentages for every body-level element. Now that all modern browsers support box-sizing: border-box (IE8+) using percentages is much safer because they include the padding/border measurements.

Percentage-based height values won't mix with fixed-heights anyway. The fixed-height will always be a different ratio to the viewport, especially when the user manually resizes.

The solution is to create your own absolutely-positioned wrapper. Browser do know how to calculate the height for an absolutely positioned element that's attached to the correct pixel offsets.

See the Pen Dynamic Height w/fixed header, scroll content by Mike Botsko (@helion3) on CodePen.

Let's start with the core HTML markup. We have a fixed-height header and the page content below:

<header>header content</header>
<div id="wrapper">
  <article id="content">
  <!-- site content -->
header { height: 60px }

So far, there's no way to tell the content element to fill the remaining height of the page. By creating our own "viewport" that's attached 60px from the top (to leave room for the header), and to the 0 edges of the left, right, and bottom - the browser will always calculate the height of this div automatically.

#wrapper {
 position: absolute;
 top: 60px;
 left: 0;
 bottom: 0; 
 ight: 0;
 overflow-y: scroll
#wrapper div { min-height: 100% }

This provides a new context in which the content's height can be set. When we set the content element to min-height: 100%, it will be exactly 100% of the remaining viewport space.

Setting overflow-y: scroll will allow the wrapper to scroll when the content exceeds this length.

It works on all browsers, including IE.