Planck mass

The reduced Planck mass isIn natural units, Einstein's gravitational coupling is $M_{\mathrm{Pl}}^{-2}=8\pi G$.

The Planck length is ${\ell }_P=\sqrt{\hslash G/c^3}$. Together with the Planck mass $m_P=\sqrt{\hslash c/G}$ it satisfies $G{m}_P/c^2={\ell }_P$.