Purpose of Review <p>This review examines the evolution of gambling-related harm (GRH) measurement over the past two decades, highlighting the shift from repurposed problem gambling severity measures to dedicated GRH instruments. It aims to clarify the importance of grounding GRH as an impact on health-related quality of life (HRQoL) and address challenges in quantifying GRH impacts.</p> Recent Findings <p>The latest generation of GRH measures, such as the Gambling Harm Scales (GHS) family, demonstrate strong psychometric properties but require benchmarking to HRQoL. Validation studies using diverse methodologies, including indirect elicitation, qualitative interviews, and expert evaluation, provide compelling evidence for the validity of these instruments in capturing meaningful differences in harm severity across the spectrum. However, challenges remain in quantifying the precise impact of GRH, particularly at lower levels of severity. Direct elicitation methods may overestimate harm due to stigma and response framing effects, while indirect methods using conventional health measures such as the SF-6D or EQ-5D may be overly conservative in their absolute estimates.</p> Summary <p>A hybrid approach, anchoring the upper severity limit using direct methods and estimating the gradient of harm using indirect methods with diverse criterion measures, offers a promising solution to quantifying GRH. Importantly, concerns over the validity of specific GHS items are largely moot, as GRH is a unidimensional construct well-indicated by a broad range of symptomatology. The key challenge lies in grounding GRH scores to HRQoL decrements, which will enable comparisons with other health conditions and resolve questions like the prevention paradox. Further empirical work and collaboration among researchers are needed to reach consensus on this fundamental issue, working towards validated and grounded measures that are necessary to inform evidence-based policy.</p>