Show HN: Free biological-age calculator from standard bloodwork (www.longevity-tools.com)

A new free tool lets anyone estimate biological age from routine blood tests: a web calculator built by Zsolt Szabo that uses biomarkers available in commercial labs and requires no sign-up. The underlying model was trained on 306,000 participants from the UK Biobank and—according to the author—delivers an ~11% relative improvement in predictive value versus the widely used Levine PhenoAge metric. A linked research paper documents the model and its performance gains. This matters because it democratizes access to a high-performing blood-based aging biomarker that’s immediately actionable for individuals, clinicians, and researchers: inputs are standard lab tests, so integration with existing clinical workflows or personal health tracking is straightforward. Key technical caveats to note are that the model is UK Biobank–trained (so cohort demographics, assay platforms, and calibration may limit portability), and external validation/clinical calibration will be important before using it for decision-making. Still, its combination of scale, improved predictive power, and free, privacy-friendly availability makes it a useful tool for longitudinal monitoring, research cohort stratification, and accelerating work on interventions aimed at improving healthspan.