# siunitx: scientific notation

I want to use scientific notation with the siunitx package. However, when I try to do it I am getting an error:

The width of a human hair is \SI{1 \times 10^{-4}}{m}.


This has always given me a LaTeX Error" invalid character '10^{-4}' in numerical input

Is there a better way to do this while continuing to use siunitx?

Thanks!

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@Caramdir - thanks for adding those tags. –  dtlussier Aug 25 '10 at 19:52
Is it is output that's important here or the input? –  Joseph Wright Aug 25 '10 at 20:28
I'm not sure what your question means. I pulled the error string directly from the output generated from building the LaTeX document. –  dtlussier Aug 25 '10 at 20:51
I wonder if you need \SI{1 \times 10^{-4}}{m} to work in the input or only to get 1 \times 10^{-4} in the output. –  Joseph Wright Aug 25 '10 at 20:52
@user766308 If you want to typeset a number without a unit, siunitx provides the \num command, e.g. \num{e-4} will print 10^{-4}. –  Torbjørn T. Dec 7 '11 at 12:34

Sure: \SI{1e-4}{\metre}.
Ok - thanks. What about a number like 10^{-4} that isn't scientific notation but has an exponent? –  dtlussier Aug 25 '10 at 20:50
\SI{e4}{\metre} –  Joseph Wright Aug 25 '10 at 20:53
@Joseph: That assumes a base of 10. What about other bases, like 3^{5}? –  Kit Jan 18 '11 at 14:33
@Kit. \sisetup{exponent-base = <whatever>} using the current release (v2) of siunitx, or \sisetup{expbase = <whatever>} with v1. –  Joseph Wright Jan 18 '11 at 15:44