Damage functions were determined for Type 304 stainless-steel mechanical property changes in yield strength and total elongation for an irradiation and test temperature of ∼480°C. The damage functions correlate the spectral effect of test reactor neutron induced changes in mechanical properties for subsequent use in predicting fluence limits for specified property level changes for reactor design studies. By propagating errors in the damage function analysis, a conservative lower bound fluence limit may be estimated. Results show that the yield strength damage function is nearly the same as the displacement cross section used as the first approximation to the damage function. The total elongation damage function shows a high energy, >4 MeV, and low energy, <10−3 MeV, enhancement of damage. Consequently, it is necessary to consider neutrons of all energies when correlating both fast and thermal test reactor data.