From http://www.jankoatwarpspeed.com/post/2008/07/09/Justify-elements-using-jQuery-and-CSS.aspx#id_b16cb791-5bd7-4bb3-abc2-dc414fc1bd07

jquery.labelautoWidth.js

$('label').autoWidth({limitWidth: 350}); 

jQuery.fn.autoWidth = function(options) 
{ 
  var settings = { 
        limitWidth   : false 
  } 
   
  if(options) { 
        jQuery.extend(settings, options); 
    }; 
     
    var maxWidth = 0; 
   
  this.each(function(){ 
        if ($(this).width() > maxWidth){ 
          if(settings.limitWidth && maxWidth >= settings.limitWidth) { 
            maxWidth = settings.limitWidth; 
          } else { 
            maxWidth = $(this).width(); 
          } 
        } 
  });   
   
  this.width(maxWidth); 
}