Electron Mass

In physics, the electron mass or mass of electron or electron rest mass one of the fundamental constants and is defined as the mass of a stationary electron. Denoted by me. The value of electron mass is also known as the invariant mass of an electron.

Electron Mass Value

Electron mass is sometimes termed as rest mass because according to the special theory of relativity mass of the object is said to vary according to the frame of reference.

Electron mass me = 9.109 ×10−31 Kilograms

The electron mass value can be expressed through various units like, electron mass in amu, electron mass in eV. Refer the table given below for units along with electron mass value-

Mass of electron


mass of electron in kg

9.10938356(11) × 10−31


mass of electron in grams

9.10938356(11) × 10−28


mass of electron in amu



mass of electron in ev



Rest Mass Of Electron

The rest mass of electron or mass of electron can be calculated from fine structure constant(α) got through spectroscopic measurements and Rydberg constant (R).

Rest Mass Of Electron formula

By using the definition of Rydberg constant we can write –

\(m_{e}=\frac{2R_{\infty }h}{c\alpha ^{2}}\)


  • me is the rest mass of electron.
  • h is the Planck Constant.
  • c is the velocity of light in vacuum.
  • R is the Rydberg constant.
  • α is the fine structure constant.

Hope you have understood about Mass of electron. Including, definition, formula, terms along with units, Rest mass of electron values, in various units like- mass of electron in kg, mass of electron in grams, mass of electron in amu, mass of electron in eV

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Practise This Question

Imagine a Carnot engine that operates between the temperatures TH 850 K and TL 300 K. The engine performs 1200 J of work each cycle, which takes 0.25 s. What is the efficiency of this engine?