This calculator is the live instrument version of a book. Every threshold, weight and dial on this site is published here first, in full, with the reasoning shown rather than just the number.
Version 1.0 — January 2026. Freely shared; please keep the authors' attribution if you pass it on.
Download the book (PDF) →Most books in this category sell a single intervention — a supplement stack, a fasting protocol, a wearable. This one is methodology first: it treats biological age as something to instrument and control, not something to intuit from how you feel, and spends more pages on how to measure honestly than on what to do about any one marker.
It is also explicit about its own limits — what each dial does not capture, where the evidence is thin, and when to stop self-experimenting and involve a clinician. The authors are the same two people named on every page of this site: an engineer and a nurse practitioner, not a brand.
189 pages across four parts. Part I sets up the engineering mindset — why healthspan is a product with measurable specs, aging as a control system, and the evidence standard the book holds itself to before a single dial is introduced.
Part II is the eight dials themselves, one chapter each — vascular, metabolic, atherogenic, inflammatory, organ, cognitive, structural and hormonal age — covering what moves each one, how fast, and a minimum-viable and advanced protocol for each.
Part III is integration: the handful of levers that move several dials at once, what to do when improving one makes another worse, a 12-week measure-intervene-retest cycle, and worked case studies.
Part IV covers epigenetic clocks and where this framework fits alongside them, decision trees for choosing a protocol, common failure modes, and red-flag stop rules — followed by eight reference appendices: lab panels, imaging, supplements with evidence tiers, a biohack ROI table, a pharmacology primer, a glossary, and full study citations by chapter.
The calculator and the eight dial pages on this site implement exactly the thresholds and weights this book describes — the engine is not a separate interpretation of the framework, it is the framework, running. The methodology page is the shorter, web-native version of Part I and II's reasoning; this book is the long-form original.
Reading the book is not required to use the calculator. It exists for the minority of readers who want the full reasoning, the citations, and the protocols in one place rather than spread across a site.
By Steve Fayzulayev & Naomi Fayzulayev, FNP-C, MSN. About the authors · Web methodology · The 8 dials.
Yes. It is a direct PDF download, not gated behind an email address — there is nothing to sign up for.
Yes. The file itself states it is a freely shared resource, version 1.0 (January 2026), and asks only that it be shared with attribution to the authors.
No. The calculator and the dial pages on this site cover the same thresholds and reasoning in web-native form. The book is for readers who want the long-form version with full citations.
Calculate your Longevity Score free →Choose a question. Answers come from this site, and nothing you open is sent anywhere.
Yes. It is a direct PDF download, not gated behind an email address — there is nothing to sign up for.
Yes. The file itself states it is a freely shared resource, version 1.0 (January 2026), and asks only that it be shared with attribution to the authors.
No. The calculator and the dial pages on this site cover the same thresholds and reasoning in web-native form. The book is for readers who want the long-form version with full citations.
Chronological age counts birthdays. Biological age estimates how old your body appears to be functioning, based on measurable biomarkers. Two people born the same year can differ by a decade or more in vascular stiffness, insulin signalling or cardiorespiratory fitness. Biological age makes that gap explicit — and unlike your birthday, it can move in either direction.
Each biomarker you enter is scored against longevity-optimised reference ranges and grouped into one of eight dials. Every dial produces its own biological age, and those are combined using fixed weights into a single composite, then expressed as a Longevity Score from 0 to 100. The weighting reflects how strongly each system predicts healthspan: structural and vascular carry the most, hormonal the least.
No. The short form contains a subset of scoring inputs plus context-only fields, and you can leave any of them blank. It is not a recommendation to obtain tests. Missing values are excluded from the calculation — never treated as zero or as 'normal'. A dial with no scored data is dropped entirely and the remaining weights renormalise.
Some inputs can be measured without bloodwork. Blood pressure needs a home cuff and waist-to-height needs a tape measure. Wearable estimates vary; the floor-based sitting-rising test carries a fall risk and should only be attempted if safe.
Both terms describe what this tool does, and which one fits depends on what you are asking. "Anti-aging" is the term most people search, and loosely means anything aimed at slowing or reversing age-related decline — this tool fits that description if you score your dials and act on what you find. "Healthspan calculator" is the more precise term: healthspan is the number of years lived without serious chronic disease or disability, and that cannot be measured directly, so this tool scores eight systems that each function as an early-warning proxy for it. Either way, the method is the same: real biomarkers, published thresholds, no vanity-metric framing.
Several popular tools ask only about habits — exercise days, sleep hours, smoking, diet quality — and return a single precise-looking age. We looked at the research behind that approach and chose not to build it. Published studies do show real, individually-measured links between specific habits and epigenetic age acceleration, but those effect sizes come from different study populations, different DNA-methylation clocks and different measurement units. Adding them together into one number is not something the underlying research actually supports — it produces a precise-looking result built on an imprecise method. Our dials use direct physiological measurements instead: a real blood pressure reading, a real VO₂ max, a real ApoB value. Several dials score from home-measurable data alone with no quiz-guessing involved — see what you can measure without a blood test, above.
Standard reference ranges describe what is common in a general population, which now includes a great deal of metabolic dysfunction. They are tuned to flag disease, not to identify what is optimal for a long healthspan. A fasting insulin of 20 µIU/mL sits inside most labs' normal range and is strongly associated with insulin resistance. This tool uses longevity-optimised thresholds instead, so a flag here means room for optimisation — not a diagnosis.