We present a simplified derivation of approximate solutions for the magnitude of, and the relations between, the three critical fields of a type II superconductor done in the spirit of the Ginzburg−Landau equations. The appearance of an unexpected equation restricting the free choice of macroscopic parameters is shown to be a direct consequence of the ’’correctness’’ of the Ginzburg−Landau theory, i.e., its physical equivalence to the microscopic theory of Bardeen, Cooper, and Schrieffer.