The Planck mass is the fundamental unit of mass in the system of Planck units. It has the value:

m_P = 2.18 × 10^-8 kg

In SI units, measurements of mass are made in kilograms (usually given the symbol kg). While the kilogram is convenient for use in everyday life, such as measuring the mass of a person or the mass of ingredients for a cake, it becomes less practical when we discuss the masses of the elementary particles such as the proton (rest mass of 1.67 × 10^-27 kg) and the electron (rest mass about 1/1800 that of the proton).

A consequence of using kilograms to measure mass is that the fundamental constants take on values that are not always convenient for including in equations:

Speed of light	c = 299792458 ms-1
Gravitational constant	G = 6.673(10) x 10-11 m3 kg-1 s-2
Plank’s constant (reduced)	= h/2π = 1.054571596(82) x 10-34 kg m2 s-1
Boltzmann constant	k = 1.3806502(24) x 10-23 kg m2 s-2 K-1

The Planck mass is derived dimensionally using combinations of these fundamental constants:

By redefining the base units for length, mass and time in terms of the Planck units, the fundamental constants have the values: c = G = = k = 1.