The Boltzmann constant provides a mapping from the characteristic microscopic energy E to the macroscopic temperature scale T = ⁠ E / k ⁠. In fundamental physics, this mapping is often simplified by using the natural units of setting k to unity. This convention means that temperature and energy quantities have the same dimensions. In particular, the SI unit kelvin becomes superfluous, being defined in terms of joules as 1 K = 1.380 649 × 10 J. With this convention, temperature is always given in units of energy, and the Boltzmann constant is not explicitly needed in formulas.