In the nonrelativistic case, electron degeneracy pressure gives rise to an equation of state of the form P = K 1 ρ, where P is the pressure, ρ is the mass density, and K 1 is a constant. Solving the hydrostatic equation leads to a model white dwarf that is a polytrope of index ⁠ 3 / 2 ⁠ – and therefore has radius inversely proportional to the cube root of its mass, and volume inversely proportional to its mass.