Biological age calculator
This is the simple version of the model inside the fjt app: answer once and see your estimated biological age.
How it is calculated
- 1It starts from your chronological age; each lifestyle signal adds or removes years.
- 2Sleep, steps and training come from the app's time model: each signal is first converted into minutes gained or lost per day, clipped to its daily cap, then converted into years (one year = 365.25 days).
- 3Ideal sleep is 7.5 hours; the further you are from it, the bigger the loss. Every 1,000 steps adds a gain. Training minutes are scaled by the moderate-intensity factor.
- 4Activity level and smoking apply directly in years. BMI comes from height and weight; above 25 and below 18.5 add years.
- 5If you enter a resting heart rate, its distance from the 62 bpm reference applies, and the VO₂max estimate uses your real heart rate.
- 6The result is clamped between a realistic floor and your chronological age + 15.
Frequently asked questions
What is biological age?
It is an estimate of how your body is functioning. A value below your chronological age means your lifestyle signals are better than average for your age.
Is the result wrong without heart rate?
No. The calculation works without it; only the VO₂max estimate then relies on age and activity, and it is labelled as estimated.
Is this a medical test?
No. The result is a statistical estimate and does not replace a diagnosis.
Is my data stored?
No. The tool runs in your browser, needs no login, and your inputs are not sent to a server.
How do I lower my biological age?
The biggest levers are consistent sleep (around 7.5 hours), more daily steps, 150+ minutes of moderate movement per week, and quitting smoking.
Sources
- Nes BM et al., Estimating VO2peak from a non-exercise prediction model: the HUNT Study, Norway (Med Sci Sports Exerc, 2011)
- NTNU World Fitness Level / Fitness Calculator
- WHO-5 Well-Being Index (WHO Regional Office for Europe)
- American Heart Association — Target Heart Rates & resting heart rate
- Cooper Institute / ACSM cardiorespiratory fitness norms
- WHO — Physical activity guidelines
This tool produces an estimate and is not a medical diagnosis. Talk to a doctor about health decisions.
Download fjt for daily tracking and detailed results
fjt turns your sleep, movement, nutrition and heart rate into time gained or lost every day, and builds a personal route for you.