Specific guidance on the size and composition of respiratory protective device (RPD) stockpiles for use during a pandemic is lacking. We explore the economic aspects of stockpiling various types and combinations of RPDs by adapting a pandemic model that estimates the impact of a severe pandemic on a defined population, the number of potential interactions between patients and health care personnel, and the potential number of health care personnel needed to fulfill those needs. Our model calculates the number of the different types of RPDs that should be stockpiled and the consequent cost of purchase and storage, prorating this cost over the shelf life of the inventory. Compared with disposable N95 or powered air-purifying respirators, we show that stockpiling reusable elastomeric half-face respirators is the least costly approach. Disposable N95 respirators take up significantly more storage space, which increases relative costs. Reusing or extending the usable period of disposable devices may diminish some of these costs. We conclude that stockpiling a combination of disposable N95 and reusable half-face RPDs is the best approach to preparedness for most health care organizations. We recommend against stockpiling powered air-purifying respirators as they are much more costly than alternative approaches. (Disaster Med Public Health Preparedness. 2015;9:313-318)