[jQuery] how to get fluid dimension of an element

[jQuery] how to get fluid dimension of an element

I have an element with 3em height.
//console.log(_$quarter.css('height'));//28.2px
//console.log(_$quarter.css('height'));//28
<a href="http://maxb.net/scripts/dndbooking/demo/">http://maxb.net/scripts/dndbooking/demo/</a>
Is there a method to obtain the real css (3em) property of this element?
thanks
Max