I have a complex js function with an equation in which I actually need to understand how much space in pixels font sizes take up.
I have noticed that some font's sizes are different depending on the font.
How is a font's size calculated? If its set to 12px, in css, what does the 12px mean? Is that 12px wide? High? Or is it a diagonal pixel measurement?
See the spec:
The font size corresponds to the em square, a concept used in typography.
Note that certain glyphs may bleed outside their em squares.