Much of the research on the patient safety risks of hospital overcrowding has focused on the emergency department, where overcrowding and increased length of stay have been linked to medication errors and other types of adverse events. This observational study sought to develop a metric of hospital system load—a multidimensional measure of overall hospital workload—and investigate the relationship between system load and adverse events. The final system load metric included measures of census, length of stay, and turnover for the emergency department, inpatient units, and operating rooms. In exploratory analyses this was correlated with several types of adverse events. Though further research will be needed to validate the system load metric, this study provides a new method to quantify system stressors that could affect patient safety.