A simple, online, self-diagnostic tool has been developed to allow students to independently and quickly measure their potential of success in a first-year general chemistry course. The online tool employs well-established performance predictors in areas such as student educational background, conceptual basics, critical thinking, mathematical skills, and problem-solving skills. This particular self-diagnostic test shows a strong correlation coefficient between the test score and the overall final grade in the course. Careful observation of correlations between sections of the diagnostic test and various components of the course suggest further refinements to the instrument and the advice we give students. (Contains 2 notes, 2 tables and 1 figure.)