Board Thread:General Discussion/@comment-26943411-20150824205605/@comment-23880286-20150827210309

1em is as big as the font size of the element. If your font size is 1px, 1em is 1px. If your font size is 2px, 1em is 2px. If your font size is 3px, 1em is 3px. And so forth.

1pt is 1/72 inch.