relation between textsize and field height?

[Tiemo Hollmann TB]

Hi,

I want to let the user change the textsize of single line fields. Now I am
looking for a formula for calculating the ideal field height, so that the
text sits centered in the height of the field. The perfect height of the
field is neither (at least not for all options) the formatted height, nor
the textsize + 2 x margins or something like this. E.G

Textsize=12, margins=8 the formattedheight is 30 and the ideal field height
is 21

Textsize=24, margins=8 the formattedheight is 46 and the ideal field height
is 46

Does anybody has a formula or an idea to get the ideal height for single
line fields? Perhaps I just don't see the obvious parameter.

Thank you

Tiemo