Normal HRV by Age: Apple Watch, SDNN & RMSSD
What is a good HRV for your age? Understand why recording length and SDNN versus RMSSD matter, and how to compare Apple Watch readings with your own baseline.
Updated September 16, 2026 · By Cortisol+ Editorial
What is a normal HRV for my age?
There is no single normal HRV range that applies to every person of the same age. A useful reference must match the metric, recording length and measurement conditions. A brief Apple Watch reading, an overnight average and a 24-hour ECG result should not be treated as interchangeable.
Shaffer and Ginsberg's review of HRV metrics and norms explains why age, recording duration and the study population affect reference values. Age-related patterns in a population do not create a diagnostic cutoff for your Watch reading.
Before using an HRV-by-age chart
| Check | Why it matters |
|---|---|
| Metric: SDNN or RMSSD | Both use milliseconds, but summarize beat-to-beat variation differently. |
| Recording duration | A short sample cannot be interpreted using a 24-hour reference range. |
| Conditions | Resting, exercising, sleeping and paced breathing are different contexts. |
| Source population | A study's participants and measurement protocol may differ from yours. |
We removed an earlier illustrative age-band table because it could be mistaken for validated Apple Watch reference ranges. We do not provide a universal “normal” number for a 30-, 40-, 50- or 60-year-old.
Is SDNN the same as RMSSD?
No. SDNN describes the spread of normal beat intervals; RMSSD describes successive interval differences. The review's metric definitions explain the distinction. Do not convert a number from one metric into the other by treating their units as proof of equivalence.
How do I check my Apple Watch HRV?
- Open Health on your iPhone and search for Heart Rate Variability.
- Inspect the dates, times and data sources behind the displayed values.
- Compare the same metric from the same source over comparable periods.
- Record context such as sleep, exercise and how you felt in a simple observation journal.
- If records are missing, follow the HRV troubleshooting checklist.
Apple describes the measurements collected by its heart sensor in its heart-rate documentation. For the wider distinction between sensor readings and calculated scores, read our Apple Watch stress guide.
Is a higher HRV always better?
No. The HRV norms review cautions that higher variability is not always a sign of better health. A wearable reading alone cannot establish your health status or explain a change.
What does Cortisol+ do with HRV?
Cortisol+ organizes available wearable signals into a wellness score and trend views. The model's baseline rules and missing-data handling are described in our methodology. It does not measure cortisol or establish that a hormone level rose or fell.
Look at the input breakdown and timestamps as well as the summary score. To compare approaches before downloading, use our Apple Watch stress-app guide.
What if my number looks low?
A chart or app score cannot determine whether you need medical care. If you have symptoms or are concerned about a persistent change, discuss the readings and their context with a qualified clinician. Do not use HRV to diagnose a cortisol disorder or change prescribed treatment.