Planck constant is 4.135667516x10^-15 (eV*s)

Planck described radiation emission as discrete packets, quantas, of energy.  Planck's constant (denoted h)  relates the wavelength to the frequency of an emission.  This constant defines the quantum of action in physics.  

Planck's constant is expressed in this equation in units of:

`eV*s`

Notes

The Planck constant, h, is specified with a standard uncertainty of `0.000 000 091 *10^(-15)` eV s

The relative standard uncertainty is: `2.2 *10^(-8)`

See Uncertainty of Measurement Results, a discussion provided by NIST of the application of uncertainty to the documented constants.  http://physics.nist.gov/cuu/Uncertainty/index.html

Interested in the physicist for whom this constant is named?  See Socratica's video on Max Plank.