e is the elementary charge, the smallest free charge. Every charge is a whole-number multiple of it: q = ne. It is exact since 2019: 1.602176634 × 10⁻¹⁹ C.
Value of e in different units
| Value | Use it when |
|---|---|
| −1.602 × 10⁻¹⁹ C | Electron. A proton carries +1.602 × 10⁻¹⁹ C. |
| 4.8 × 10⁻¹⁰ esu (statcoulomb) | CGS units. |
Formulas that use e
- q = ne
- 1 eV = 1.602 × 10⁻¹⁹ J
- F = Nₐe = 96 485 C/mol
- e/m = 1.76 × 10¹¹ C/kg
Its dimensional formula is worked out on the dimensional formula of electric charge page.
Other constants
- Gas constant (R): 8.314 J mol⁻¹ K⁻¹
- Planck's constant (h): 6.626 × 10⁻³⁴ J s
- Avogadro's number (Nₐ): 6.022 × 10²³ mol⁻¹
- Speed of light (c): 3 × 10⁸ m/s
- Charge of an electron (e): 1.602 × 10⁻¹⁹ C
- Mass of an electron (mₑ): 9.109 × 10⁻³¹ kg
- Mass of a proton (mₚ): 1.673 × 10⁻²⁷ kg
- Mass of a neutron (mₙ): 1.675 × 10⁻²⁷ kg
- Universal gravitational constant (G): 6.674 × 10⁻¹¹ N m² kg⁻²
- Acceleration due to gravity (g): 9.8 m/s²
- Boltzmann constant (k): 1.381 × 10⁻²³ J/K
- Faraday constant (F): 96 485 C/mol
- Permittivity of free space (ε₀): 8.854 × 10⁻¹² C² N⁻¹ m⁻²
- Permeability of free space (μ₀): 4π × 10⁻⁷ T m/A
- Rydberg constant (R): 1.097 × 10⁷ m⁻¹
- Stefan–Boltzmann constant (σ): 5.67 × 10⁻⁸ W m⁻² K⁻⁴
- Wien's constant (b): 2.898 × 10⁻³ m K
- Bohr radius (a₀): 0.529 Å
- Molar volume of a gas at STP (Vₘ): 22.4 L/mol
The full list, searchable, is on the physical constants page.
Questions students ask
What is the value of charge of an electron?
e = 1.602 × 10⁻¹⁹ C. In other units: −1.602 × 10⁻¹⁹ C; 4.8 × 10⁻¹⁰ esu (statcoulomb).
What is e in physics and chemistry?
e is the elementary charge, the smallest free charge. Every charge is a whole-number multiple of it: q = ne. It is exact since 2019: 1.602176634 × 10⁻¹⁹ C.
Which value of e should I use?
−1.602 × 10⁻¹⁹ C: Electron. A proton carries +1.602 × 10⁻¹⁹ C. 4.8 × 10⁻¹⁰ esu (statcoulomb): CGS units.
What is the dimensional formula of charge of an electron?
See the dimensional formula of charge of an electron, worked out step by step on its own page.