Materials selection is a key part of aircraft design. The materials index is used to numerically rank materials for a particular function, for example, the strength-to-weight ratio selects minimum-weight structural ties that satisfy a strength constraint. However, the ordinary materials index uses nominal or allowable material properties and does not reliably propagate manufacturing variability or statistical characterization. This work introduces the precision materials index (PMI) to rigorously account for both factors. Counterintuitive results from the PMI are demonstrated. Several case studies demonstrate new analyses enabled by the PMI (making supplier comparisons and exploring materials and process scenarios) and how the analytic PMI concept can be complemented with statistical modeling to analyze more complex structures, namely, a composite laminate plate.