We present SA-6, a six-item psychometric scale for assessing people’s security attitudes that we developed by following best practices. We identify six scale items based on theoretical and empirical research with sufficient response variance, reliability, and validity in a combined sample (N = 478) from Amazon Mechanical Turk and a university-based study pool. We validate the resulting measure with a U.S. Census-tailored Qualtrics panel (N = 209). SA-6 significantly associates with self-report measures of behavior intention and recent secure behaviors. Our work contributes a lightweight method for (1) quantifying and comparing people’s attitudes toward using recommended security tools and practices, and (2) improving predictive modeling of who will adopt security behaviors. Presentation to the Usenix Symposium on Usable Privacy and Security (SOUPS 2019), Aug. 12, 2019, Santa Clara, CA, USA.