The present work examines the accuracy of self-reports of study time for college students. In a 10-week Mechanical Engineering course, 99 college students accessed their textbook, homework solutions, graded work, and lecture slides via custom software that recorded objective measures of reading time. In addition, the students provided subjective judgments of the time they spent reading these materials. Comparisons between the objective and subjective measures reveal that students significantly overestimated time with the textbook, homework solutions, graded work, and lecture slides, with higher performing students overestimating to a lesser degree. The difference between objective and subjective judgments of study time correlated significantly and negatively with final course grade for the textbook (r = -0.31), homework solutions (r = -0.39), and lecture slides (r = -0.24), but not for graded work (r = -0.05). This study calls into question the utility of self-report data in studies of student study habits, and showcases the value of objective technology-based measures of such habits.