H1-H6 font sizes in HTML

Question

In HTML (and in typography in general, I suppose), there appears to be some defined sizes for H1-H6 -elements.

Ie., if the baseline font size is 16px (or 100%), then h1

Answer 1

It is browser-dependant, as other say.

On the other side, there is a rule in typography to set font sizes: if the base font has size X, the larger fonts should grow exponentially; the usual way is to have sizes X*sqrt(2), X*sqrt(2)^2, X*sqrt(2)^3 and so on, but you can change the base.

However, computer fonts have some special requirements.

They used to be provided in a bitmap form only (so the sizes were fixed), and even when provided in vector form -- some formats preferred some special sizes: divisible by 2 or 5 (this was f.e. the case with Amiga's old vector fonts... Agfa Intellifont?).

Even now font engines like integer sizes more, because their hinting algorithms work better.

And people seem to got used to the values chosen because of these technical restrictions, even though font engines got much better now.