The SI unit of Planck's constant is the joule second (J·s). It is a physical constant that relates the energy of a photon to the frequency of its electromagnetic wave, commonly expressed as approximately 6.626×10−346.626\times 10^{-34}6.626×10−34 joule-seconds. This unit can also be represented in base SI units as kg⋅m2⋅s−1\text{kg}\cdot \text{m}^2\cdot \text{s}^{-1}kg⋅m2⋅s−1 since 1 joule equals 1kg⋅m2⋅s−21\text{kg}\cdot \text{m}^2\cdot \text{s}^{-2}1kg⋅m2⋅s−2 and the second is multiplied onto it.
