Determining the Days of Supply for Class 1 Inventory Aboard U.S. Navy Ships

Abstract

This research addresses inconsistencies in calculating days of supply (DoS) for Class I inventory aboard U.S. Navy vessels, a challenge that threatens operational readiness in contested logistics environments. To achieve this, we analyzed nine months of historical consumption data from the Food Service Management System (FSM3) across 14 ship classes, examining the alignment between current DoS calculation methods and actual at-sea consumption patterns. Our analysis uncovered key issues: the reliance on dollar-value-based calculations that ignore consumption variability, the application of uniform assumptions across diverse ship classes, and disparities between reported DoS estimates using different Navy systems. To address these challenges, we developed the Supply Select App, an interactive R-based tool that provides fleet commanders with accurate Food Item Code (FIC)-level usage data tailored to specific ship classes. The app employs three core metrics: average daily consumption, projected DoS, and projected order quantity, which are derived from empirical consumption records rather than financial approximations. This research highlights the urgent need for data-driven approaches in naval sustainment, focusing on operational autonomy and resilience in communications-denied environments. The Navy’s adoption of evidence-based logistics tools is crucial to maintain combat readiness and mission continuity while ensuring accurate sustainment of its deployed personnel.