Calculator Inputs
The page stays in a single content stream, while the form fields use a responsive grid: three columns on large screens, two on medium, and one on mobile.
Example Data Table
| Profile | Age | Baseline lnRMSSD | Sleep | Stress | Load | Sample RR Pattern | Possible Result |
|---|---|---|---|---|---|---|---|
| Recovered athlete | 28 | 4.45 | 8.1 h | 3 | 4 | Stable, slightly rising intervals | High score and strong readiness |
| Busy office worker | 36 | 4.10 | 6.2 h | 7 | 6 | Moderate variation with stress effects | Midrange score and caution |
| Fatigued trainee | 31 | 4.30 | 5.4 h | 8 | 9 | Compressed intervals, lower variability | Low score and recovery focus |
Formula Used
Core interval metrics
Mean RR = ΣRR / n
Mean HR = 60000 / Mean RR
SDNN = √(Σ(RR - Mean RR)² / (n - 1))
RMSSD = √(Σ(ΔRR)² / (n - 1))
SDSD = standard deviation of successive RR differences
pNN50 = beats with |ΔRR| > 50 / (n - 1) × 100
Log-transformed recovery metric
lnRMSSD = ln(RMSSD)
Age comparison reference
Age Reference lnRMSSD = max(2.8, 4.75 − 0.015 × Age)
HRV score model
Core Recovery = 50 + 25 × tanh((lnRMSSD − Baseline lnRMSSD) / 0.35)
Age Component = 10 × tanh((lnRMSSD − Age Reference) / 0.30)
Sleep Component = clamp((Sleep Hours − 7) × 4, −10, 10)
Stress Component = clamp((5 − Stress Level) × 2.5, −12, 12)
Load Component = clamp((6 − Training Load) × 2, −10, 10)
HRV Score = clamp(Core Recovery + Age Component + Sleep + Stress + Load, 0, 100)
This scoring model blends interval variability, baseline deviation, age context, sleep, stress, and training load. It is useful for fitness tracking and readiness trends, not for diagnosing disease.
How to Use This Calculator
- Measure your RR intervals in milliseconds from a chest strap, wearable, or exported session file.
- Enter your age and your usual baseline lnRMSSD. Use a rolling average from past good-recovery mornings if possible.
- Add sleep hours, stress level, and training load for the same day.
- Paste at least 10 valid RR intervals into the textarea.
- Press Calculate HRV Score to see results above the form.
- Review the score, zone, variability metrics, autonomic state, and RR plot.
- Export your result as CSV or PDF to track daily changes.
FAQs
1. What does the HRV score represent?
It summarizes recovery readiness using RR variability, your personal baseline, age context, sleep, stress, and training load. A higher score usually suggests better recovery and capacity for harder effort.
2. Why does the calculator use RMSSD and lnRMSSD?
RMSSD is widely used for short-term parasympathetic activity. lnRMSSD makes the data more stable and easier to compare across days, which improves trend tracking and scoring consistency.
3. How many RR intervals should I enter?
At least 10 valid intervals are required, but more is better. Short morning readings with clean data generally produce more stable variability metrics and more reliable trend comparisons.
4. Can I use smartwatch exports?
Yes, if the export gives raw or beat-to-beat RR intervals in milliseconds. Cleaner readings from chest straps often reduce noise and improve the quality of HRV calculations.
5. What baseline lnRMSSD should I use?
Use your personal rolling baseline from rested days. Many people average several morning readings over one to three weeks, then update the baseline gradually as fitness and lifestyle change.
6. Why did my score drop after poor sleep?
Sleep loss often raises sympathetic strain and lowers variability. This calculator includes sleep hours directly, so reduced sleep can decrease the final score even when interval metrics look only slightly lower.
7. Is a high HRV score always better?
Usually yes for recovery, but context matters. A sudden spike can also follow unusual conditions, measurement differences, or illness recovery. Trends and consistency are more useful than one isolated score.
8. Is this calculator medical advice?
No. It is a fitness and readiness tool. It can help monitor recovery patterns, but it does not diagnose heart rhythm problems, disease, or any medical condition.