Arithmetic competence is crucial for navigating modern society and maintaining independence. It relies on domain-general and domain-specific cognitive skills, as well as subjective factors. Given its importance, understanding how these factors shape adult arithmetic proficiency is essential. This study investigated demographic, cognitive, and subjective influences on various arithmetic skills throughout adulthood, including both younger and older individuals. In total, 134 adults aged 20–68 completed computerized tasks assessing simple calculations, exact and approximate complex calculations, and arithmetic principles, alongside neuropsychological testing and self-ratings on math anxiety, math self-concept, attitudes toward mathematics, and the frequency of engagement with numbers. The results indicate that accuracy varied by task, with approximate calculations being the most challenging. Self-ratings showed low math anxiety but moderate-to-high math self-concept, positive attitudes, and moderate engagement with numbers. Age correlated only with arithmetic principles; however, interference inhibition and engagement with numbers, not age, best predicted performance. Executive functions correlated solely with approximate calculations and arithmetic principles, while subjective measures were related to all arithmetic tasks. The regression analyses indicate strong interrelationships, particularly among calculation tasks. The findings highlight the multifaceted nature of arithmetic competence and suggest it remains stable in adulthood, with age-related declines only evident in arithmetic principles, likely due to declining executive functions.