Get the tag offset
<html> <head> <title>Overflow</title> <style type="text/css"> #div1 { width: 700px; height: 150px } #div2 { width: 600px; height: 100px; overflow: auto } </style> <script type="text/javascript"> function switchContent() { document.write(document.getElementById("div2").offsetHeight); } </script> </head> <body> <p> <a href="javascript:switchContent();">Switch</a> </p> <div id="div1"> <p>p1</p> </div> <div id="div2"> <p>Smaller item.</p> </div> </body> </html>