In natural units everything is expressed in units of mass or energy. (c= 1 = \(\bar{h}\)). Even \(L^{-1} or t^{-1}\)= units of energy (ev or better MeV or GeV).

Eamples:

1. Convert \(1 fm^{-1}\) to MeV. We know that, 1eV=1.6 x 10e-19 C (J/C) =1.6e-19 J

We know that E/(\(\bar{h}c\) has units of \(fm^{-1}\)), so we can divide by it.

\[ \begin{eqnarray} \frac{1eV}{\overline{h}.c}= \frac{1.6e-19}{6.63e-34 J s * 3 * 10^{8} \frac{m}{s}} \\ \frac{1ev}{\overline{h}c}=8.049 * 2*\pi*10^{5} m^{-1} \\ \text{In natural units: \overline{h}=c=1 , so } \\ 1eV=2\pi*10^{5} * 8.049 m^{-1} \\ 1m^{-1}=197.7 * 10^{-9} eV \\ 1fm^{-1}=197.7 MeV \end{eqnarray} \]