Five ways to measure biological age

Written by Steve Fayzulayev. Clinically reviewed by Naomi Fayzulayev, FNP-C, MSN.

Last reviewed 2026-11-09. See our editorial policy and methodology.

"Biological age" is not one test. At least five genuinely different methods exist, with different evidence behind each, and most calculators online use only one of them while implying they have covered the whole picture.

1. Perceived facial age

How old you look to a stranger is a real, published biomarker of aging — not folk wisdom. A 2009 Danish twin study (Christensen et al., BMJ) rated the perceived age of nearly 1,000 twin pairs over 70 and found that the twin who looked older was significantly more likely to die first, independent of their shared genetics and chronological age. Perceived facial age also correlated with physical function, cognitive function and leukocyte telomere length in the same study.

We do not score facial age. Scoring it well requires either a trained human panel (as the original study used) or an AI vision model making a judgement call from a photo, and we deliberately keep this tool's biomarker-based scoring method free of that kind of model-dependent output — see <a href="/compare/chatgpt-lab-results">why a fixed method matters for tracking</a>.

2. Physical function tests

Grip strength, the floor-based sitting-rising test and walking speed have been studied as measures of physical function. The floor test carries a fall risk and should only be attempted if safe.

See <a href="/guides/biomarkers-without-a-blood-test">measuring biological age without a blood test</a> for exactly which tests, and how to do them in a way that produces a repeatable number rather than a one-off guess.

3. Hearing

Age-related hearing loss is linked to outcomes beyond hearing itself: a 2012 study (Lin & Ferrucci, Archives of Internal Medicine) found hearing loss independently associated with a higher risk of falls in older adults, and a separate 2011 study (Lin et al., Archives of Neurology) linked hearing loss to a higher risk of incident dementia. Both associations held after adjusting for age and other factors.

This tool does not score hearing — it would require an audiometric test, not a questionnaire, to measure honestly, and a self-reported "can you hear well?" input would not carry the same evidence behind it as the cited studies.

4. Composite biomarker panels

Blood pressure, lipids, glucose, inflammatory markers and similar measurements, combined by a published formula into a composite score. This is the family this tool belongs to — see <a href="/guides/what-is-biological-age">what biological age is</a> for how the method works and what it can and cannot tell you.

5. DNA methylation clocks

Epigenetic clocks (Horvath, PhenoAge, GrimAge, DunedinPACE) measure chemical marks on DNA from a blood or saliva sample. They are the most research-validated method for predicting mortality at a population level, and the most expensive and least actionable for tracking your own change quarter to quarter.

See <a href="/guides/epigenetic-age-vs-biological-age">epigenetic age vs biological age</a> for a full comparison of what each clock was trained on and why they disagree with each other.

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Frequently asked questions

How to find your biological age?

"Biological age" is not one test. At least five genuinely different methods exist, with different evidence behind each, and most calculators online use only one of them while implying they have covered the whole picture.

What does this guide cover?

This guide covers: 1. Perceived facial age; 2. Physical function tests; 3. Hearing; 4. Composite biomarker panels; 5. DNA methylation clocks.

All guides

Not medical advice. These are longevity-optimised reference ranges, which are deliberately stricter than standard clinical "normal" values. A value outside them does not mean you have a disease. Speak to a qualified healthcare professional before changing medication, supplements or training. Full disclaimer.
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How to find your biological age?

"Biological age" is not one test. At least five genuinely different methods exist, with different evidence behind each, and most calculators online use only one of them while implying they have covered the whole picture.

What does this guide cover?

This guide covers: 1. Perceived facial age; 2. Physical function tests; 3. Hearing; 4. Composite biomarker panels; 5. DNA methylation clocks.

What is biological age?

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.

How is the Longevity Score calculated?

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.

Do I need all 53 biomarkers?

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.

What can I measure without a blood test?

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.

Is this an anti-aging calculator? Is it a healthspan calculator?

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.

Why don't you have a quick quiz that skips biomarkers entirely?

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.

Why are your 'optimal' ranges stricter than my lab's normal range?

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.

Why not just upload my labs to ChatGPT?

For understanding a single result, do — a frontier chat model is genuinely good at that, often clearer than most medical sites, and it handles markers no fixed tool covers. The limitation is different from the one most people assume. A language model produces a plausible response rather than a computed one, so the same panel can score differently on different days. That is fine when exploring an idea and disqualifying when measuring change, because you cannot tell how much of a difference is you and how much is the method. Use both: a chat model to understand, a fixed instrument to track.

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