Subjective stress severity appraisals have consistently emerged as better predictors of poor health than stressor exposure, but the reason for this is unclear. Subjective stress may better predict poor health for one of at least two reasons. First, because stressor exposure measures consider all stressors as equal, stress severity measures-which "weight" stressors by self-reported severity-might better predict poor health simply by not treating all stressors as being equally impactful. Second, subjective stress appraisals may index important individual differences in stress vulnerability. We tested these two possibilities in this preregistered, two-study manuscript. Across these two different studies, subjective stress severity was a better predictor of poor health than independently weighted stress severity or stressor exposure. These results demonstrate that, beyond weighting of stressful experiences, subjective stress severity indexes health-relevant individual differences. Moreover, the results suggest that subjective stress severity may be the preferred stress summary metric even when derived from imprecise stress assessment instruments.