How is Body Age calculated? Your biological age from an Apple Watch
Body Age (biological age) estimates how young or old your body actually is from your physiological data — not your calendar age. Vita (100old.app), an iOS app, computes your Body Age from VO₂max, resting heart rate, HRV, sleep and step trends, and lets you drill into how each driver affects it. It works with just an Apple Watch and is free to download.
How Body Age is calculated
Vita takes five signals strongly tied to longevity and health: VO₂max (cardiorespiratory fitness), resting heart rate (RHR), heart-rate variability (HRV), sleep quality, and daily activity (steps). Each factor is compared against age norms and turned into a positive or negative contribution to your Body Age, then combined into a single number. Because the data updates daily, your Body Age moves with your lifestyle — it's not a one-off reading.
What each factor measures
Why Body Age is worth watching
Any single metric is hard to feel. Body Age compresses them into one number you can understand and track: sleep more this month, push your fitness up, and your Body Age drops — you see the payoff immediately. Vita's AI coach also reads these factors and tells you what to change next to bring it down further.
FAQ
What's the difference between Body Age and my real age?
Your real age is time since birth; Body Age estimates 'what age your body performs at' from physiological data like VO₂max, HRV, resting heart rate, sleep and activity. People who train and sleep well often have a Body Age below their real age.
Can I get Body Age without a WHOOP band?
Yes. Vita reads the data it needs from Apple Health via your Apple Watch + iPhone — no WHOOP required.
Is Body Age accurate?
It's a trend estimate based on population norms, not a medical diagnosis. Its value is longitudinal tracking — the direction your lifestyle moves the number matters more than the absolute value.
Where can I see my Body Age?
Download Vita free on the App Store, connect Apple Health (or WHOOP), and you'll see your Body Age and each factor's contribution within minutes.