Question about unit conversion and feature request.

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I frequently need to convert units and I find sage very useful in doing that. However, sage does not support conversion to natural units which is frequently used in particle physics. So I have to keep multiplying expressions by $\hbar$ and $c$ in each notebook. Is there a more efficient way to convert quantities from SI to natural units. Does anyone have a idea so that sage can automatically identify the length, mass and time dimension and multiply by appropriate power of $\hbar$ and $c$. Also how difficult would it be to include this feature in sage?

Let me give a brief explanation of what natural units are. All the quantities in natural units are generally expressed a power of energy and $c$ and $\hbar$ are set to one. So one over length is equal to energy etc.