We show that the energy gap for the BCS gap equation is Ξ=μ(8e-2+o(1))exp(π2μa)in the low density limit μ→ 0. Together with the similar result for the critical temperature by Hainzl and Seiringer (Lett Math Phys 84: 99–107, 2008), this shows that, in the low density limit, the ratio of the energy gap and critical temperature is a universal constant independent of the interaction potential V. The results hold for a class of potentials with negative scattering length a and no bound states.