BEHIND THE NUMBERS
Physical constants
Exact SI defining constants. These values are definitions, so they have no measurement uncertainty.
| Constant | Value | Unit | Precision | Definition |
|---|---|---|---|---|
| Speed of light in vacuum | 299792458 | m/s | exact | SI defining constant, 2019 |
| Planck constant | 6.62607015e-34 | J·s | exact | SI defining constant, 2019 |
| Elementary charge | 1.602176634e-19 | C | exact | SI defining constant, 2019 |
Sources
- NIST: Fundamental physical constants ↗ · 2026-10-07