jQuery.px

1em within different contexts of font-size…

Default
font-size: x-small
font-size: 20px
font-size: 1in
font-size: larger
font-size: 1cm
font-size: 1mm
font-size: 100%
font-size: 2.54cm

Different unit sizes, within context of font-size: 10px

Different unit sizes, within context of font-size: 20px

Different unit sizes, without context (<body> has font-size: 14px)

Different quantities