# How can I set default font size to [bp] instead of [pt] in order to use Lyx with XeTex?

I want to use the [bp] font size for the whole document in Lyx 2.0.4 for compilation with XeLatex. My LaTex preamble looks like this: \usepackage{fontspec} \usepackage{xunicode} \usepackage{xltxtra} \date{}. If I specify \documentclass{article}[12bp] I get these errors: LaTex Error: Two \documentclass or \documentstyle commands and LaTex Error: Missing \begin{document}.

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I would just use 12pt (\documentclass[12pt]{article}), that's quite close, but well supported. –  Heiko Oberdiek Nov 27 '12 at 22:20
If I do that I get LaTex Error: Two \documentclass or \documentstyle commands. But I want to use [bp], as I said, not [pt]. Is that even possible (avoiding the error, of course)? –  riderplus Nov 27 '12 at 22:23
The error: consult the documentation of LyX. Using bp instead of pt: You would have to redefine lots of macros (all font size commands, ...), because pt is the standard unit in TeX, not bp. –  Heiko Oberdiek Nov 27 '12 at 22:25
I couldn't find anything related to that errror. So there's no easy way of using bp instead of pt. That's a pity, MSWord uses bp and it would make it difficult for me to write my thesis, I would end up filling less space. –  riderplus Nov 27 '12 at 22:31
@riderplus The reduction in font size is marginal. Hopefully, your are evaluated by content, and not turned down because the thesis is a line too short. –  Sveinung Nov 27 '12 at 22:48

\documentclass[12pt]{article}

you have the [ after the class name so it is not taken as an optional argument but just as normal text, so you get an error that you can not have text before \begin{document} The difference in size between a 12pt font and a 12bp font is no difference at all, you get more difference between two nominally 12pt size fonts of different design, The label attached to a font size is only indirectly related to any actual measurement. 12bp is 12.045pt the difference in height of two nominally 12pt fonts can easily be more than that.
Thank you, but that doesn't answer my question. How can I work with [bp] instead of [pt]? The MSWord font is clearly larger than TeX's [pt]. –  riderplus Nov 28 '12 at 19:34
I've tried putting in the preamble of a LyX 1.6.5 \documentclass[12pt]{article} and it gives the same error. –  riderplus Nov 28 '12 at 19:58