Best biological age tracking apps in 2026: what to look for

"Biological age" now shows up in lab portals, smartwatch apps, and supplement stores. The same words can mean very different things. Before you pick an app, it helps to know what kind of number it gives you, and how it was made.

Three kinds of biological age

Blood-based scores. These use a routine blood panel. The best known is PhenoAge, published by Levine and colleagues in 2018. It takes nine standard markers plus your age in years and runs them through a fixed formula. The maths is public, so anyone can check it. Delta uses this method and calls the result Adaptive Age.

Epigenetic clocks. These read DNA methylation from a blood or saliva kit sent to a lab. They are a different kind of measurement, usually more expensive per test, and results take weeks. They measure something related but not the same as a blood-panel score, so the two should not be compared number to number.

Wearable scores. Several watch and ring makers now show an "age" built from heart rate, heart rate variability, sleep, and activity. These update often and cost nothing extra, but they are estimates from signals that move day to day. Delta shows a wearable-only estimate too, called Vitals Age, and labels it as an estimate with a wider range.

Five questions to ask any biological age app

1. Can you see the formula? A published method with public coefficients can be checked. A secret "proprietary algorithm" cannot.
2. Is it deterministic? The same inputs should always give the same number. If a language model writes your score, two runs can disagree.
3. What happens when a marker is missing? Some tools quietly fill gaps with population averages. Your number is then partly about someone else. Delta refuses to score and tells you which marker is missing.
4. How are units handled? Glucose in mg/dL is about 18 times the same value in mmol/L. A tool that guesses units will eventually produce a nonsense age. Delta only accepts units on an allowlist and rejects the rest.
5. Where does your data live? A health record on a company server is a record you do not control. Delta keeps your history on your phone, with no account and no sign-in.

How Delta fits

Delta is a free app for iPhone and Android. You add a blood report as a PDF or a photo, confirm the values, and it computes your Adaptive Age on your device. The same dashboard brings in Apple Health or Health Connect, training, nutrition, sleep, body composition, and mood, so your blood results sit next to the rest of your data.

It is a wellness app, not a medical device. It will not tell you what to take, and it does not treat one number as a verdict. The useful part is the trend: one panel is a position, the next panel shows the direction.

A simple way to start

Pull your most recent blood panel. Check that it has the nine markers listed in our guide to calculating biological age from a blood test. If it does, you already have what you need. If it does not, ask for the missing ones at your next routine test.