Defining Constants and Corresponding Units
The Core SI Constants
| Defining Constant | Symbol | Numerical Value | Unit |
|---|---|---|---|
| hyperfine transition frequency of Cs | \(\Delta \nu_{\text{Cs}}\) | \(9\ 192\ 631\ 770\) | \(\text{Hz}\) |
| speed of light in vacuum | \(c\) | \(299\ 792\ 458\) | \(\text{m}\ \text{s}^{−1}\) |
| Planck constant | \(h\) | \(6.626\ 070\ 15\ \times 10^{−34}\) | \(\text{J}\ \text{s}\) |
| elementary charge | \(e\) | \(1.602\ 176\ 634 × 10^{−19}\) | \(\text{C}\) |
| Boltzmann constant | \(k\) | \(1.380\ 649 \times 10^{−23}\) | \(\text{J}\ \text{K}^{−1}\) |
| Avogadro constant | \(N_A\) | \(6.022\ 140\ 76 \times 10^{23}\) | \(\text{mol}^{−1}\) |
| luminous efficacy | \(K_{cd}\) | \(683\) | \(\text{lm}\ \text{W}^{−1}\) |
SI Brochure: The International System of Units (SI) (2019). Bureau International des Poids et Mesures. Ninth Edition. Table 1 (The Seven Defining Constants of the SI and the Seven Corresponding Units They Define). pg. 128.
See Also
- SI Defining Constants. Provides a graphical overview of the table above, and a more detailed overview of the relationship between the base units and the defining constants.