More and more libraries are investigating the possibility of breaking apart or unbundling their “Big Deal” publisher packages. In doing so, libraries acknowledge and ready themselves for the possibility of a significant portion of journal use shifting to interlibrary loan (ILL), and attempt to estimate what this shift from subscription to the ILL mode means in terms of costs. This study investigates three years of ILL usage data for 1651 journals prior to undertaking subscriptions and then Counting Online Usage of Networked Electronic Resources (COUNTER) usage for these same journals over a three year subscription period. The results suggest a predictive ratio of ILL requests to COUNTER uses and COUNTER uses to ILL requests.