https://doi.org/10.1351/goldbook.E02032
The elementary charge, \(e\), is one of seven fixed constants defining the International System of Units, the SI, with \(e = 1.602\ 176\ 634\ \times 10^{-19}\ \text{C}\). The elementary charge \(e\) corresponds to a coupling strength of the electromagnetic force via the fine-structure constant and is considered as a fundamental constant of nature.