Popular font type and font size in HTML body in web design

According to studies, the popular font type is 'Arial' and.font size 13px in HTML body.
In CSS:
font-family: arial, sans-serif;
 font-size: 13px; 
color: black;
The conversion between between em, px, pt and percent in font size is as follows:
1em = 12pt (point) = 16px (pixel) = 100% (percent).
1 point =1/12 inch
"percent %" is recommended for fully scalable of mobile devices and for accessibility.
such as
 html { font-size: 150%; )
or
body { font-size: 150%; )