Elementary charge
= 1.602 176 634 × 10−19 C
- Value
- 1.602 176 634 × 10−19 C
- Standard uncertainty
- exact
- Relative uncertainty
- exact
- Status
- Exact since the 2019 SI redefinition
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# elementary charge, CODATA 2022 (NIST)
e = 1.602176634e-19 # C, exact
# SciPy: scipy.constants.physical_constants['elementary charge']What it is
The electric charge of one proton; an electron carries −e. Every free particle seen so far has a charge that is a whole multiple of e (quarks carry thirds of it but are never seen alone). Since 2019 its value is exact and defines the ampere: one ampere is a flow of 1/(1.602 176 634 × 10⁻¹⁹) elementary charges per second.
This is one of the seven defining constants of the SI. Its value was measured until the CODATA 2017 special adjustment fixed it, and it has been exact since the new definitions took effect on 20 May 2019.
Equations
- Faraday constant
- Josephson constant
- von Klitzing constant
In other units
| Unit | Value | |
|---|---|---|
| e elementary charge | 1 | exact |
Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display.
How the value changed, 1998–2022
Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart). Diamonds mark adjustments in which the value was exact.
Relative uncertainty
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 1.602 176 634 × 10−19 | exact | exact |
| 2018 | 1.602 176 634 × 10−19 | exact | +1.3 σ of 2014 |
| 2014 | 1.602 176 6208(98) × 10−19 | 6.1 × 10−9 | +1.6 σ of 2010 |
| 2010 | 1.602 176 565(35) × 10−19 | 2.2 × 10−8 |
“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).