Search the table by name or symbol to find a constant, read its value and SI unit, and copy the plain number or the full expression into your calculation or lab report.
Since the 2019 SI redefinition, seven defining constants have exact values with no uncertainty: the speed of light, the Planck constant, the elementary charge, the Boltzmann constant, the Avogadro constant, the caesium hyperfine frequency and the luminous efficacy. Everything else, including G, is measured and carries an uncertainty.
G is notoriously hard to measure because gravity is extremely weak and cannot be shielded, so it is known to only about five significant figures — far fewer than atomic constants, which are known to ten or more.
The CODATA recommended values, which are the internationally agreed set used in physics and chemistry. Each entry lists the symbol, the value in SI units and the unit itself, and you can copy any value with one click.