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

*E*_{p}= 1.96 × 10^{9}JIn SI units, measurements of energy are made in Joules (usually given the symbol

**J**). The Joule is convenient for everyday usage, such as measuring the energy produced by eating different types of foods (eating 1 gram of a carbohydrate provides around 16,000 J of energy) or determining the energy requirements of a light globe (a 60 W globe uses 60 J every second). We can also write Joules in terms of the units of length, time and mass:1 Joule = 1kg m

^{2}s^{-2}A consequence of SI units is that the fundamental constants take on values that are not always convenient for including in equations:

Speed of light *c*= 299792458 m s^{-1}Gravitational constant *G*= 6.673(10) x 10^{-11}m^{3}kg^{-1}s^{-2}Plank's constant (reduced) = *h*/2π = 1.054571596(82) x 10^{-34}kg m^{2}s^{-1}Boltzmann constant *k*= 1.3806502(24) x 10^{-23}kg m^{2}s^{-2}K^{-1}The Planck energy is found using Einstein's famous formula relating energy and mass:

*E*, with the Planck mass defined as:_{p}= m_{p}c^{2}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.