Mathematical competency is related to performance in introductory statistics courses and may be a roadblock to successful course completion. We developed a new measure (Math Assessment for College Students, MACS) of basic mathematics skills that improves upon measures previously used in undergraduate settings. The MACS is freely available and contains items not typically included on standardized measures of mathematical ability. We administered the 44-item MACS to 414 undergraduate psychology statistics students, and used a multiple correspondence analysis to eliminate 14 items, resulting in a 30-item measure with strong psychometric properties. MACS scores showed statistically significant moderate correlations with a commonly used standardized measure of basic mathematics skills and with overall statistics course grade. We discuss the utility of the MACS and how the MACS may help course instructors identify areas of mathematical deficiency that require remediation.