Physics Constants Reference

Searchable reference table of fundamental physical constants — speed of light, Planck's constant, Boltzmann constant, elementary charge, Avogadro's number, and more

Physical Constants (25)

Symbol	Name	Value	Unit
c	Speed of light in vacuum	2.99792458 × 10⁸	m/s
G	Gravitational constant	6.67430 × 10⁻¹¹	m³ kg⁻¹ s⁻²
h	Planck constant	6.62607015 × 10⁻³⁴	J·s
ħ	Reduced Planck constant	1.054571817 × 10⁻³⁴	J·s
e	Elementary charge	1.602176634 × 10⁻¹⁹	C
ε₀	Vacuum permittivity	8.8541878128 × 10⁻¹²	F/m
μ₀	Vacuum permeability	1.25663706212 × 10⁻⁶	H/m
k_e	Coulomb constant	8.9875517923 × 10⁹	N·m²/C²
Φ₀	Magnetic flux quantum	2.067833848 × 10⁻¹⁵	Wb
k_B	Boltzmann constant	1.380649 × 10⁻²³	J/K
N_A	Avogadro constant	6.02214076 × 10²³	mol⁻¹
R	Gas constant	8.314462618	J/(mol·K)
σ	Stefan-Boltzmann constant	5.670374419 × 10⁻⁸	W/(m²·K⁴)
m_e	Electron mass	9.1093837015 × 10⁻³¹	kg
m_p	Proton mass	1.67262192369 × 10⁻²⁷	kg
m_n	Neutron mass	1.67492749804 × 10⁻²⁷	kg
u	Atomic mass unit	1.66053906660 × 10⁻²⁷	kg
a₀	Bohr radius	5.29177210903 × 10⁻¹¹	m
α	Fine-structure constant	7.2973525693 × 10⁻³	(dimensionless)
R_∞	Rydberg constant	1.0973731568160 × 10⁷	m⁻¹
μ_B	Bohr magneton	9.2740100783 × 10⁻²⁴	J/T
g	Standard gravity	9.80665	m/s²
atm	Standard atmosphere	101325	Pa
eV	Electron volt	1.602176634 × 10⁻¹⁹	J
ly	Light-year	9.4607304725808 × 10¹⁵	m