Physical Constants

symbol name value unit
c  
speed of light in a vacuum
 
299,792,458   m/s
G  
gravitational constant
 
6.67384 × 10−7 N m2/kg2
h  
planck's constant
 
6.62606957
 4.135667516
× 10−34
× 10−15
J s
eV s
hc  

 
1.98644521
1239.84193
× 10−25
 
J m
eV nm
h/2π
reduced planck's constant
dirac's constant
1.054571726
 6.58211928
× 10−34
× 10−16
J s
eV s
ε0 electric constant
permitivitty of free space
vacuum permitivitty
8.854187817 × 10−12 C2/N m2
μ0 magnetic constant
permeability of free space
vacuum permeability
× 10−7 T m/A
e  
elementary charge
 
1.602176565 × 10−19 C
me  
electron mass
 
9.10938291
0.510998928
0.00054857990946
× 10−31

 
kg
MeV
u
mp  
proton mass
 
1.672621777
938.272046
1.00727646812
× 10−27

 
kg
MeV
u
mn  
neutron mass
 
1.674927351
939.565379
1.00866491600
× 10−27

 
kg
MeV
u
mu  
atomic mass constant
 
1.660538921
931.494061
1
× 10−27

 
kg
MeV
u
NA  
avogadro's constant
 
6.02214129 × 1023 1/mol
k  
boltzmann's constant
 
1.3806488 × 10−23 J/K
R  
gas constant
 
8.3144621   J/mol K
σ  
stefan-boltzmann constant
 
5.670373 × 10−8 W/m2K4
b  
wien displacement constant
 
2.8977721
58.789254
  mm/K
GHz/K
g  
standard gravity
 
9.80665   m/s2
atm  
standard atmosphere
 
101,325   Pa
H0
hubble constant*
 
70.8
2.29
 
× 10−18
km/s/Mpc
s−1
Physical constants
Source: NIST * exception NASA