Biological Age Calculator
Find out how old your body really is. Use the no-labs Fitness Age model, or the research-grade PhenoAge model from a standard blood test.
Try an example — click to load & calculate
How the Fitness Age model works (formula)
Your Fitness Age starts from your chronological age and applies evidence-based offsets from each marker, comparing you to population norms for your age and sex:
- VO₂ max (strongest weight): scored against FRIEND/Cooper Institute percentile norms — every ~1 ml/kg/min above or below your age-sex median shifts your fitness age by roughly 0.35 years.
- Waist-to-height ratio: values above 0.5 add years; below 0.5 are protective.
- Resting heart rate and systolic blood pressure: each standard deviation from the healthy range adds/subtracts years.
- Grip strength (if entered): a validated mortality marker scored against age-sex norms.
- Sleep, exercise minutes, smoking: lifestyle modifiers based on cohort hazard ratios.
The offsets are summed, lightly weighted toward VO₂ max (the single strongest predictor of all-cause mortality), and added to your chronological age. This is a transparent, defensible composite — not a clinical diagnosis.
How the PhenoAge model works (Levine 2018 formula)
PhenoAge uses a Cox/Gompertz mortality model published by Dr. Morgan Levine and colleagues (Aging, 2018), validated in 11,432 NHANES III adults. We compute a linear score from your 9 biomarkers plus age, convert it to a 10-year mortality score, then translate that into an age-equivalent:
xb = -19.907 - 0.0336·albumin + 0.0095·creatinine + 0.1953·glucose
+ 0.0954·ln(CRP) - 0.0120·lymph% + 0.0268·MCV
+ 0.3306·RDW + 0.00188·ALP + 0.0554·WBC + 0.0804·age
M = 1 - exp( -exp(xb)·(exp(120·γ)-1)/γ ), γ = 0.0076927
PhenoAge = 141.50225 + ln(-0.00553·ln(1-M)) / 0.090165
Units matter. The published Levine coefficients are calibrated to SI units, so we convert your entries internally before applying the formula: albumin g/dL → g/L (×10), creatinine mg/dL → µmol/L (×88.42), glucose mg/dL → mmol/L (÷18.0182), and CRP mg/L → mg/dL (÷10) before taking the natural log. ALP stays in U/L and WBC in 10³/µL. RDW carries the largest coefficient (0.3306), making it the single strongest driver of the score.
Frequently asked questions
What is biological age and how is it different from chronological age?
Chronological age is simply how long you have been alive. Biological age estimates how old your body is physiologically, based on measurable markers of fitness, metabolism, inflammation and organ function. Two people aged 45 can have biological ages of 38 and 52 depending on their health.
How accurate is a biological age calculator?
The PhenoAge model is research-grade — validated on over 11,000 adults and shown to predict mortality and disease better than chronological age alone. The Fitness Age model is a transparent estimate built on validated norms (VO₂ max, grip strength, waist-to-height) but is not a clinical diagnosis. Both are best used to track your own trend over time.
Can I calculate biological age without a blood test?
Yes. The Fitness Age tab needs no labs — just your VO₂ max (available from most smartwatches), resting heart rate, waist, height and blood pressure, with optional grip strength and lifestyle inputs.
Which blood markers do I need for PhenoAge?
Nine: albumin, creatinine, fasting glucose, hs-CRP, lymphocyte %, MCV, RDW, alkaline phosphatase and white blood cell count. These come from a standard CMP, CBC with differential and an hs-CRP test.
Can I lower my biological age?
Evidence suggests yes. Improving VO₂ max, building strength, reducing visceral fat, controlling glucose and inflammation, sleeping 7–9 hours and not smoking are all associated with a younger biological age. A 2021 randomized trial reported a ~3-year PhenoAge reduction over 8 weeks of diet and lifestyle changes. Re-test every 3–6 months to track progress.
What is a good biological age result?
A biological age more than 5 years below your chronological age is associated with roughly 20–30% lower all-cause mortality in population studies. Anything below your real age is favorable; above it signals accelerated aging worth addressing.
This calculator is for educational purposes only and is not medical advice or a diagnosis. The PhenoAge model is based on Levine et al. (2018), Aging (Albany NY). Always consult a qualified healthcare professional for medical decisions.
Creator
Shakeel Muzaffar is the Founder and Editor-in-Chief of MultiCalculators.com, bringing over 15 years of experience in digital publishing, product strategy, and online tool development. He leads the platform's editorial vision, ensuring every calculator meets strict standards for accuracy, usability, and real-world value. Shakeel personally oversees content quality, formula verification workflows, and the platform's commitment to publishing tools that are genuinely useful for students, professionals, and everyday users worldwide.
Areas of Expertise: Editorial Leadership, Digital Publishing, Product Strategy, Online Calculators, Web Standards
