Planck Mass

In physics, the Planck mass, denoted by $m_P$, is the unit of mass in the system of natural units known as Planck units. It is defined so that $\approx 1.2209 \times 10 GeV/c_0 = 2.17651(13) \times 10 kg$, (or $21.7651 \mu g$), where $c_0$ is the speed of light in a vacuum, $G$ is the gravitational constant, and $\hbar$ is the reduced Planck constant. Particle physicists and cosmologists often use the reduced Planck mass, which is $\approx 4.341 \times 10 kg = 2.435 \times 10 GeV/c$. The added factor of $1/{\sqrt{8\pi}}$ simplifies a number of equations in general relativity. Quantum effects are typified by the magnitude of Planck's constant.