Infection preventionists play a key role in the prevention of healthcare-associated infections (HAI). This article describes the creation and validation of a calculator that uses risk and complexity factors to generate individualized infection prevention and control (IPC) staffing ratios. Based on data submitted by 390 US hospitals, including size and case mix index, the calculator estimated nearly 80% of respondents had lower than expected IPC staffing. Hospitals with below-expected staffing levels were more likely to have higher standardized infection ratios.