A subcritical droplet must make a rare thermal fluctuation from the metastable basin over the free-energy barrier . Its probability carries the Boltzmann factor , so the nucleation rate has the Arrhenius form
For a volume containing order one candidate subcritical droplet, the waiting time for a supercritical droplet and subsequent macroscopic growth is therefore
up to an algebraic kinetic prefactor. This is the Arrhenius nucleation time.