Web Typography cinch box to type - css

Question

When using a <h1> tag for example, is there a reusable formula for getting the outer border of that element to PERFECTLY follow edges of the type? In theory I would expect this to work:
h1{
display: block;
font-family: sans-serif;
font-size: 38px;
line-height: 100%;
height: 38px;
}
So the line height is set to be the same as the absolute text height, which is also the height of the block. However this never works. Here is an example of what does work for sans-serif 38px;
h1{
display: block;
font-family: sans-serif;
font-size: 38px;
line-height: 28px;
height: 35px;
}
Here is another working example.
h1{
display: block;
font-family: sans-serif;
font-size: 25px;
line-height: 19px;
height: 22px;
}
This is all well and good, but it has to be calculated manually in firebug each time. There is no formula I can find to do this.
Additionally, it would be nice if any solution also worked with #font-face fonts, but I understand there is more to take into account there. (like the top alignment that only occurs on Mac).
Does such a formula exist? Is it possible to write one? How about some LESS CSS fancyness?

Answer 1

I agree with #ToddBFisher in the comment, and at this point for me it's more of an usability issue. Consider people can also vary the font sizes in their browsers... in that case using ems would be better. But browsers also render font differently, so something that looks amazing in a mac will look pixelated in a pc. If you want something to look perfect, use images.
Check this other question for more info on line-height: How to achieve proper CSS line-height consistency
Or this one: CSS Line-Height Guide
You can also check the usability stack for discussions about these things: https://ux.stackexchange.com/ There are pretty amazing posts in there.