The mass of an electron is extremely small, and it's typically measured in units of atomic mass units (amu) or electron volts (eV).

Here are the commonly used values:

* 9.10938356 × 10⁻³¹ kilograms (kg)

* 5.48579909 × 10⁻⁴ amu

* 0.511 MeV/c² (where c is the speed of light)

It's important to note that the mass of an electron can be expressed in different ways depending on the context and the required level of precision.