CSS Proportional Letter Spacing

I’m aware that by dividing font-size into line-heigh it’s possible to come up with a multiple which can be used to express line-height. This value contains no measurement unit (e.g. em, rem, px), and its advantage is that it’s totally scalable based on what size the client displays the font at.

My question is, is there an equivalent method for letter-spacing, and how does it work?

Cheers,
simon

There is a letter-spacing property which allows you to stretch letters apart or contract them. Not sure if that’s what you are looking for, but it’s worth trying. E.g.

h1 {letter-spacing: 2em;}