@RaymondLim it's a 10:1 ratio for ems:pixel.  The code you refer to is a 1:0.1 ratio which equates to 10:1.  If the units are in ems, we need to multiply them by 10 to convert them into pixels. I think keeping everything in pixels is the best bet even if we are using ems because, I *think*, the calculated font-size always comes back in pixels regardless.