I don't think so but here is somethign I found about a combobox's font "ratio" which uses GetFontInfo() function:
https://github.com/esoui/esoui/blob/...ommon.lua#L574
Maybe you can adopt this code somehow if you get the label's font info in any way
Or, depending on your language, you could always overwrite the label's font with a selected one (LAM menu combobox with font entries e.g.) and le the user choose the font + size maybe.