# How to create fractional SI units (\SI{…}{\sqrt{s}})?

I want to express a variable that has "square root units", i.e. 0.8e-3 m/sec^1.5.

I have tried to use the SI package:

\SI{0.8e-3}{\radian\per\second\sqrt{\second}}


However, this does not work. It only works in cases like this:

\SI{42}{\second}


Is there a good way of expressing "square root units" or similar? Or is it necessary to use a workaround like:

\num{0.87e-5}\,$\mathrm{m}/\mathrm{s}\sqrt{\mathrm{s}}$


Arbitrary powers can be given using \tothe:
\documentclass{article}