Measuring performance is a key component in advancing the rule of law. Quantitative indicators are useful tools to evaluate performances, draw attention to issues, establish benchmarks, monitor progress, and evaluate the impact of interventions or reforms. Despite their uses, however, to date quantitative performance indicators have played only a limited role in the rule of law field. In part, this limited use reflects both the dearth of suitable quantitative rule of law indicators and the challenges inherent to their use. In this paper, we describe many of the different ways quantitative assessments of the rule of law are used and constructed, and outline some of the challenges this entails. To begin with, we discuss five key reasons why indicators are useful for advancing the rule of law. Next, we discuss four important questions to consider whenever using indicators and also underscore the importance of using indicators carefully. We conclude by offering two examples as illustrations.