<!DOCTYPE html> <html> <body> <div id="x" style="background: lightgreen; height: 3em; width: 400px; padding: 4px;"> <div style="text-indent: 40%; width: 200px; background: yellow;">X</div> </div> <script> var x = document.getElementById('x'); x.offsetWidth; x.style.width = '500px'; </script> </body> </html>