Online Tool Store
HRV Log
Log daily heart rate variability readings and see the rolling baseline, so a single low morning is read against your own normal range.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Health & Fitness
HRV Log
Frontend preview — no upload or external service.
Baseline view
Reading 48 ms against a 7-day baseline of 56 ms — 14% below, the second consecutive low day, which is the pattern worth noticing rather than either day alone.
How the HRV Log works
- Measure at the same time each morning, in the same position; HRV moves enough with posture and time of day to swamp any real signal otherwise.
- Log the value and let the rolling baseline build over a few weeks.
- Read deviations from your own baseline, never against someone else's numbers.
The method
HRV measures variation in the interval between heartbeats; RMSSD, the most common metric, is the root mean square of successive differences between beats.
RMSSD = √( mean( (RR interval difference)² ) ), in milliseconds
Absolute values differ enormously between people — 30 ms can be normal for one person and a warning for another — so only the deviation from your own baseline is interpretable.
FAQ
Why is my HRV so different from a friend's?
Because absolute HRV varies with age, genetics, and measurement method. Comparing across people is meaningless; comparing against your own rolling baseline is not.
What makes HRV drop?
Poor sleep, alcohol, illness, hard training, and stress, usually with a day's lag. A single low reading tells you little; two or three in a row is a pattern.
Is HRV a health diagnostic?
No. It is a rough recovery signal used in training. Persistent unexplained changes are a reason to see a doctor, not to self-diagnose from a chart.
How we compare
| Feature | Online Tool Store | A paper log | A subscription health app |
|---|---|---|---|
| Rolling personal baseline | ✓ | Manual | Yes |
| Metric clearly labelled | ✓ | ✓ | Sometimes |
| Data stays on your device | ✓ | ✓ | ✗ |
| Automatic device sync | ✗ | ✗ | ✓ |
HRV Log insists on your own baseline as the reference, because absolute HRV numbers mean almost nothing across different people.