# Where does the constant of Planck $6.6\times10^{−34}$ J ⋅ s come from?

I've read that this number is made out of the mass or mass equivalent of any atomic particle equal to ($9.10939 \times 10^{-31}$ kg or electron mass) x ($2.42631 \times 10^{-12}$ m or electron Compton wavelength) / (Particle wavelength).

But where are those numbers coming from? Can someone explain where the constant exactly stands for?

• I'm not sure I understand "where are those numbers coming from" - where does Newton's gravitational constant, or the Avagadro constant "come from", for instance? Commented Nov 27, 2016 at 16:17
• @ACuriousMind Good questions too. If I want to know the energy of a photon I have to multiply the frequency with h. But why has h this value? It looks that for the mass the electron is taken and I don't know where this waselength come form. But why these parameters and not something else. Commented Nov 27, 2016 at 16:42
• Possible duplicate: physics.stackexchange.com/q/144262/50583 Commented Nov 27, 2016 at 16:43

Your title mentions Planck's constant. Planck introduced his constant when he posited that $$E=hf$$ That is, that energy is proportional to frequency. The constant of proportionality, Planck's constant, is required to convert between our unit for frequency and our unit for energy.
The numerical value reflects our man-made systems of units, and not any fundamental property of nature. In fact, a convenient system of units sets $h=1$, thus using identical units for energy and frequency.
You also ask about the Planck mass and Planck length. They are quantities of unit mass and length constructed from the fundamental constants $h$, $c$ and $G$. Their numerical values reflect man-made systems of units, and in convenient systems, they may be set to one.