Biological Age Calculator
Estimate your "fitness age" — how your everyday habits stack up against your real age — from your resting heart rate, activity, sleep and smoking. A motivational mirror, not a verdict.
⚠ This is an educational "fitness age" estimate from lifestyle habits — not a real biological age, epigenetic clock or medical test (those need bloodwork or lab assays). Read it as motivation and direction, not a diagnosis or a reason to worry.
Your habits track younger than your age — about 4 years. The markers driving that (a strong resting heart rate, fitness, sleep) are exactly the ones worth protecting. Keep the trend, don't chase a number.
Adjustments are modest, capped and transparent — a four-question model can’t see your genetics or medical history. This is not a prediction of lifespan or a diagnosis. The value is the direction you can move it, not the exact number — and not anxiety over it.
Move the number, calmly
The inputs here — resting heart rate, fitness, sleep — are exactly what ONDA Life tracks over time. See them trend in the right direction instead of fixating on one daily figure.
Download ONDA Life on the App Store →Sources & methodology
This is a lifestyle/"fitness age" estimate, not an epigenetic clock or a clinical biological age — those require bloodwork, DNA-methylation assays or a lab VO₂max test. It starts from your chronological age and shifts it using four modifiable markers with well-established links to all-cause mortality: cardiorespiratory fitness/activity (the strongest lever; Mandsager 2018, Nes 2011), resting heart rate (≈+9% mortality per +10 bpm; Zhang 2016), sleep duration (a U-shaped risk) and smoking. The adjustments are deliberately modest and transparent — shown broken down by driver — and capped, because no four-question model can capture genetics, medical history or your full life. Read it as a motivational mirror of your current habits, not a prediction or diagnosis. The point is the direction you can move it, not the exact figure — and definitely not anxiety over it.
- [1] Nes BM, Janszky I, Wisløff U, et al. (2011). Estimating V̇O2peak from a nonexercise prediction model: the HUNT Study, Norway. Medicine & Science in Sports & Exercise, 43(11):2024–2030.
Basis of the "fitness age" concept — estimating fitness (and an age equivalent) from non-exercise lifestyle markers.
- [2] Mandsager K, Harb S, Cremer P, et al. (2018). Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Network Open, 1(6):e183605.
Large cohort (122,007) showing fitness is inversely associated with mortality with no upper limit — why activity weighs heaviest here.
- [3] Zhang D, Shen X, Qi X (2016). Resting heart rate and all-cause and cardiovascular mortality in the general population: a meta-analysis. CMAJ, 188(3):E53–E63.
Meta-analysis (1.2M people): each +10 bpm resting heart rate ≈ +9% all-cause mortality — the basis for the RHR adjustment.
Common questions
How is biological age calculated here?
This tool gives a "fitness age" style estimate: it starts from your real age and adjusts it using four modifiable markers tied to longevity in the research — activity/fitness, resting heart rate, sleep and smoking. It is transparent (you see each driver) and intentionally conservative. It is not an epigenetic clock or a medical test.
Is this my real biological age?
No — and be wary of anything online that claims to give you a precise one. True biological-age measures use DNA-methylation "clocks", blood biomarkers or a lab VO₂max test. This is an educational estimate of how your lifestyle habits stack up against your chronological age, useful for motivation and direction, not diagnosis.
What lowers your biological age the most?
Cardiorespiratory fitness is the single biggest modifiable lever — a large study (Mandsager 2018) found higher fitness linked to lower mortality with no upper limit of benefit. A lower resting heart rate, consistent 7–8.5 hours of sleep, and not smoking all help too. Encouragingly, fitness and resting heart rate improve within weeks of training.
My result looks older than my age — should I worry?
No. It is a snapshot of changeable habits, not a verdict on your health or lifespan, and a four-question estimate can’t see your genetics or medical history. Treat a higher number as information, not alarm: every input is something you can move, and the direction of travel matters far more than a single figure. If you have real health concerns, see a clinician.
Why does resting heart rate affect the estimate?
A lower resting heart rate generally reflects a fitter, more efficient heart and stronger parasympathetic tone. A meta-analysis of over a million people (Zhang 2016) found each 10 beats-per-minute higher resting heart rate was associated with roughly 9% higher all-cause mortality, so it is a meaningful, easy-to-measure marker — and one you can lower with aerobic training.