Many decision-makers have emphasized the importance of leveraging patient experience data to measure unmet need. However, there is no standardized, patient-centric unmet need measure that formalizes how the value judgements inherent in such a measure should be made. Several initiatives have identified measuring unmet need as one of the primary uses of patient preference data. After reviewing how decision-makers define unmet need, this paper proposes that a thresholding method could be used to generate a standardized, patient-centric, disease-agnostic, quantitative unmet need estimate, length of life equivalent (LOLE). LOLE would address some of the limitations of current methods, including facilitating capture of the impact of disease beyond health-related quality of life, and being more sensitive to the impact of a disease on patients. However, the acceptability of LOLE raises questions for decision-makers, including: Is length of life equivalence the best common metric in which to express unmet need? Is it appropriate to rate a disease as having no unmet need if patients are unwilling to trade off life expectancy for improvements in their quality of life? Can LOLE be estimated for more complex disease profiles? Is thresholding the appropriate method to use to estimate LOLE? How should LOLE be integrated into decision-making, including the level of LOLE that defines different levels of unmet need? Further work could usefully address these questions with decision-makers.