Explanation
The electron is a stable particle and a key component of the atom. When at rest (not in motion), it has a definitive and constant mass, and this rest mass is used in many equations in physics. Mass can be thought of as stored energy, as it is related to energy through the law of massenergy equivalence.
Particles consist of a variable count of wave centers (K) that reflect incoming waves (inwaves) and create spherical outwaves that are responsible for its standing waves. A special particle appears at K=10 matching the electron’s rest energy and mass. Electron rest mass is energy without consideration of wave speed (without c^{2 }in the equation). Mass is simply standing, longitudinal waves of energy.
See also: Electron Energy
Derivation – Electron Mass
The electron’s rest mass can be derived classically from the Planck mass, Planck length, electron radius and fine structure constant. In wave format, it is derived from the Longitudinal Energy Equation where K=10 (ten wave centers) and mass is represented as energy without wave speed (c^{2}). Electron mass is calculated as inwaves and outwaves that create standing waves to the electron’s classical radius where the waves become traveling in form again.
Classical Constant Form

Wave Constant Form 
Using classical constants  Using energy wave constants 
Calculated Value: 9.1094E31
Difference from CODATA: 0.000%
Calculated Units: kg
Alternative Derivation
An alternative derivation in classical form is shown with the magnetic constant and elementary charge. This version shows the consistency of energy and mass equations in classical format, as explained on the page for Coulomb’s constant.
Its value was calculated and shown to match the known value in the Summary of Calculations table. The derivation of this constant is available in the Fundamental Physical Constants paper.