Calculate your biological age from blood markers
The Bortz Age calculator estimates your biological age from up to 25 blood markers – free, without sign-up and entirely in your browser.
- 100% free – no sign-up, no account, no payment details
- Runs locally in your browser – blood values are never sent or stored
- Based on Bortz et al. 2023 (Communications Biology) – coefficients disclosed
- No product sales and no lab referrals on this page
Research-based estimate – not a medical diagnosis.
My Bortz Age: Benedikt Keck's blood panel as a worked example
What does a Bortz Age calculation with real blood values look like? For this worked example I used my own blood panel from 19 September 2025. My chronological age at that point was 34.57 years. The model estimates a Bortz Age of 19.49 years.
My Bortz Age
19.49
years – at a chronological age of 34.57 years
- Chronological age
- 34.57 years
- Bortz Age
- 19.49 years
- Age difference
- −15.08 years
- Markers used
- 21 / 25
mathematically about 15 years and 1 month younger than the chronological age – a model-based estimate, not a medical statement about health status.
The example values are filled into the form locally in your browser only.
Calculator and methodology built and reviewed by Benedikt Keck, longevity expert at Longevity Hackers.
Last content review: August 2026
Core markers
These six values are required for the calculation.
Other names
Crea, serum creatinine
Other names
Cys-C, cystatin-C
Other names
GGT, γ-GT, gamma-glutamyl transferase
Other names
red cell distribution width, RDWThe model uses RDW-CV in %. RDW-SD in fL cannot be used directly.
Other names
ALAT, SGPT, alanine aminotransferase
Other names
25-OH vitamin D, calcidiol, 25(OH)D3
No biomarkers entered yet
25 missing values are replaced with the UK Biobank reference mean
Your entries are processed exclusively in your browser and are discarded when you leave or reload the page.
What is the Bortz Blood Age?
The Bortz Blood Age estimates biological age from 25 selected blood biomarkers plus an age calibration term. It was published in 2023 in Communications Biology by a group led by first author Jordan Bortz – not to be confused with the longevity author Walter Bortz. The model estimates an age-equivalent mortality risk: it answers which age your blood profile statistically corresponds to. It does not directly measure cellular age or life expectancy.
How the calculation works
Each biomarker – log-transformed where required – is compared with the mean of the reference cohort. The deviation is multiplied by the published coefficient and summed up. Together with the age calibration this yields the Blood Age Acceleration (BAA). Your Bortz Age is your chronological age plus BAA. Every step runs locally in your browser; no values are stored or transmitted.
Bortz Age vs. PhenoAge
In the original publication the Full ENC model reached a C-index of 0.778 versus 0.750 for PhenoAge in the same cohort. That is a moderate difference in mortality-risk discrimination within a single cohort – not proof of general superiority and not a percentage accuracy claim. PhenoAge uses nine markers, the Bortz model 25, covering kidney, liver, blood count and inflammation axes among others.
Calculate PhenoAge from 9 blood markersLimits of the model
The development cohort comprised 306,116 UK Biobank participants aged roughly 38 to 73 years, about 95% of them white. UK Biobank is subject to a healthy-volunteer bias and external validation remains limited. Setting missing markers to the reference mean is a practical simplification, not the imputation used in the paper. Some coefficients run counter to clinical intuition; they are statistical weights inside a multivariate model, not medical target values.
What does my result mean?
What matters is not the absolute number but the gap to your chronological age. The ranges below describe model uncertainty, not medical cut-offs and not a diagnosis.
| Gap to chronological age | How to read it |
|---|---|
| more than 5 years younger | Your blood profile statistically matches a clearly younger age. Still double-check that every value and unit was entered correctly. |
| −5 to +5 years | Within model uncertainty. A gap of this size cannot be meaningfully interpreted from a single measurement. |
| 5 to 10 years older | Notable. Common drivers are inflammation markers, kidney or liver values. The per-marker contributions show which values dominate. |
| more than 10 years older | Clearly notable. Discuss the underlying lab values – not the calculator output – with your doctor. |
A single measurement says little. The number becomes informative as a trend across several blood draws at the same lab.
Biological age tests: the four common approaches
"Testing your biological age" can mean very different things. The four common approaches measure different things, so their numbers are not comparable.
| Approach | Basis | What it is good for |
|---|---|---|
| Blood marker models | Routine lab values weighted with coefficients from large cohorts (Bortz, PhenoAge). | Transparent, cheap and repeatable over time – quality depends on your blood panel. |
| Epigenetic tests | DNA methylation at thousands of sites, read out by a clock such as DunedinPACE or GrimAge. | Scientifically the most developed option, but paid and with varying reproducibility between labs. |
| Questionnaire calculators | Self-reported smoking, exercise, diet, sleep and stress. | A useful prompt for reflection, but it measures behaviour, not body values. |
| Body composition scales | Body composition and estimated basal metabolic rate, processed by a manufacturer formula. | Reports a "metabolic age" – not comparable with a blood-based biological age. |
This calculator belongs to the first category: lab values only, with published coefficients. It does not replace an epigenetic test or a medical examination.
Biological, metabolic and chronological age
Chronological age counts years since birth. Biological age estimates from measurements which age your body statistically matches – here from blood markers. The "metabolic age" shown by many body-composition scales is derived from body composition and estimated basal metabolic rate using proprietary formulas. It is not comparable to a blood-based biological age and should not be treated as the same metric.
Does the calculator work for women and men?
Yes. In the authors’ calculation the sex term does not enter the individual acceleration value, which is why the calculator does not ask for sex. Reference ranges of individual markers – haemoglobin, ferritin or creatinine, for example – still differ between women and men in practice. For judging a single lab value, your lab’s sex-specific reference range remains the relevant benchmark.
Methodology and sources
This calculator implements the Full ENC (elastic net, Coxnet) model from Bortz et al., Communications Biology 2023, with the published coefficients and means. The age calibration equals the difference of the two age coefficients in the publication.
Why is there no sex field?
In the authors' published worked example the sex term deliberately does not enter the individual acceleration value (BAA). A sex field would therefore not change the result and is not asked for here.
Sources
- Bortz J. et al., “Biological age estimation using circulating blood biomarkers”, Communications Biology 6, 1089 (2023).
- Public reference code by the authors for blood biomarker age estimation (coefficients and means).
- Zenodo archive of the authors’ repository (DOI 10.5281/zenodo.8392642).
- Supplementary Information of the publication (PDF, Springer Nature).
Independent implementation of the Full-ENC coefficients published by Bortz et al. Longevity Hackers is not affiliated with Humanity Inc. or the study authors.
Privacy
All inputs stay in your browser. There is no transmission to a server, no storage and no analysis of your blood values.