Physical constants

List of physical constants, expressed in SI units

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What is a physical constant

A physical constant is a quantity in nature that is universally invariant, remaining unchanged across various physical processes and conditions. These constants play a crucial role in the formulation of physical laws and theories, serving as the fundamental building blocks that govern the behaviour of the universe. Physical constants describe properties of elementary particles, interactions, and forces, providing a framework for understanding the natural world.

List of physical constants

Constant	Symbol	Value	Copyable	Units
Speed of light	$$c$$	$$2.99792458 \cdot 10^8$$	2.99792458e8	$$m \cdot s^{-1}$$
Electric permittivity	$$\varepsilon_0 = \frac{1}{\mu_0 c^2}$$	$$8.8541878128 \cdot 10^{−12}$$	8.8541878128e-12	$$F \cdot m^{-1}$$
Magnetic permeability	$$\mu_{0} = 4 \pi 10^{-7}$$	$$1.25663706212 \cdot 10^{−6}$$	1.25663706212e-6	$$N \cdot A^{-2} \ or \ H \cdot m$$
Coulomb constant	$$k_e = \frac{1}{4\pi \varepsilon_0}$$	$$8.9875517923 \cdot 10^9$$	8.9875517923e9	$$N \cdot m^2 \cdot C^{-2}$$
Boltzmann constant	$$k_B$$	$$1.380649 \cdot 10^{−23}$$	1.380649e-23	$$J \cdot K^{-1}$$
Planck constant	$$ h $$	$$6.62607015 \cdot 10^{−34}$$	6.62607015e-34	$$J \cdot s$$
Reduced Planck constant	$$\hbar = \frac{h}{2\pi}$$	$$1.054571817 \cdot 10^{−34}$$	1.054571817e-34	$$J \cdot s$$
Avogadro number	$$N_A$$	$$6.02214076 \cdot 10^{23}$$	6.02214076e23	$$mol^{-1}$$
Elementary charge	$$e$$	$$1.602176634 \cdot 10^{−19}$$	1.602176634e-19	$$C$$
Electron mass	$$m_e$$	$$9.1093837015 \cdot 10^{−31}$$	9.1093837015e-31	$$kg$$
Proton mass	$$m_p$$	$$1.67262192369 \cdot 10^{−27}$$	1.67262192369e-27	$$kg$$
Neutron mass	$$m_n$$	$$1.67492749804 \cdot 10^{−27}$$	1.67492749804e-27	$$kg$$
Faraday constant	$$F=N_Ae$$	$$9.64853321233100184 \cdot 10^4$$	9.64853321233100184e4	$$C \cdot mol^{-1}$$
Vacuum impedance	$$Z_0$$	$$3.76730313668 \cdot 10^2$$	3.76730313668e2	$$\Omega$$
Gravitation constant	$$G$$	$$6.67430 \cdot 10^{−11}$$	6.67430e-11	$$m^3 \cdot kg^{-1} \cdot s^{-2}$$
Elettronvolt	$$eV$$	$$1.602176634 \cdot 10^{−19}$$	1.602176634e-19	$$J$$
Gas constant	$$R$$	$$8.314462618$$	8.314462618	$$J K^{-1} mol^{-1}$$