Planck units

Planck units are a set of physical units based upon Planck constant and other fundamental constants, one type of natural units. They have the advantage in that they eliminate the physical constants in some physics equations, simplifying the equations and reducing the required math in using the equations. Planck units are often discussed regarding physical limits inherent in modern physics: the Planck units for two quantities, Planck length and Planck time, do reflect minimal possible amounts according to current physical laws. However, the motivation for Planck units is not these minimums, and other Planck are within or greater than the range of the typical units we use everyday.

tP ≡ √(ℏG/c5)
lP ≡ √(ℏG/c3)
mP ≡ √(ℏc/G)
EP ≡ mPc2
TP ≡ EP/KB

• t_P - Planck time (which is about 5.39 × 10^-44 s).
• l_P - Planck length (about 1.62 × 10^-35 cm).
• m_P - Planck mass (not extremely small: about 2.18 × 10^-5 g, roughly that of a millimeter of human hair, and according to some laws, the minimum possible mass of a black hole, i.e., a Planck hole).
• E_P - Planck energy (moderate: about 1.9561 × 10⁹ J, the energy from burning about 16 gallons of gasoline; it is literally the energy equivalent of the above-defined Planck mass).
• T_P - Planck temperature (extremely large: about 1.41678516 × 10³² K, and by some theories, the maximum possible temperature, or maximum for which current physical rules apply, sometimes termed absolute hot).
• ℏ - reduced Planck constant.
• G - gravitational constant.
• c - speed of light in a vacuum.
• K_B - Boltzmann constant.