Adult numeracy is underresearched especially regarding numeracy practices. Research shows general correlations between numeracy skills and the use of these skills, indicating that low proficient groups use their skills less often than others do. Earlier research also shows correlations of low numeracy skills and practices with low income. Both results feed stereotypes that vulnerable subgroups--with low numeracy proficiency or a low monthly budget--would not calculate much and this would even cause their complicated income situation. Findings of this article show that the tighter the budget is the more likely vulnerable subgroups are to monitor it by frequent calculations of prices, costs, or budgets. This article connects representative Programme for the International Assessment of Adult Competencies data from the German data set with a local sample of people with lowest income. Findings show that vulnerable subgroups calculate more often than other parts of the population, but they mostly do without technical devices.