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`h = 6.626070150 * 10^-34 J*s`

6.62607015E-34

**Planck constant (J*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. The constant defines the quantum of action in physics.

Planck's constant is expressed in this equation in units of Joule seconds (J•s)

Planck's theory asserted that energy was transferred in units known as quanta in the ratio employed in Plank's Equation. Plank's Equation is:

where:

- E is energy in Joules
- h is Planck's Constant
- f is the frequency

Note the following relations are also true:

where:

- E = energy of light
- f = frequency
- h = Planck's Constant
- c = Speed of Light in a vacuum

In 2018 when analyzed by the CODATA Task Group on Fundamental Constants, the measurements produced a final value of *h* of 6.626070150 × 10-34 kg?m2/s, with an uncertainty of 10 parts per billion. If the SI is redefined as expected in November of 2018, this will be the exact value of Planck’s constant which will define other SI units including the kilogram.

See Uncertainty of Measurement Results, a discussion provided by NIST of the application of uncertainty to the documented constants.

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