Background: College is a period of life when many young adults are exposed to or engage in substance use; however, it is useful to put substance use among college students in to context by examining the number of college students who start using or use substances on an average day. Method: Combined 2011 to 2014 National Surveys on Drug Use and Health (NSDUHs) data provides estimates of substance use initiation and past month substance use among persons aged 18 to 22 by full-time and part-time college student status. Results: Findings in this report show that, on an average day for both full-time and part-time college students, alcohol and marijuana were the substances most frequently initiated and the most frequently used. Conclusion: Highlighting the number of college students who are initiating or using substances on an average day may help when addressing substance use on college campuses.