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HRV Score Calculator — Heart Rate Variability

Enter your rMSSD or SDNN from any wearable (Oura, WHOOP, Garmin, Apple Watch). Get your age-sex percentile, autonomic nervous system balance, lifestyle impact score, and personalized recovery guidance.

HRV Metric

SDNN is converted to an rMSSD equivalent (× 0.6) so your score is always comparable to rMSSD norms.

from your wearable
ms
Biological Sex
yrs
ms

Found in WHOOP, Oura, Garmin Connect apps. Enables recovery status vs. your personal baseline.

Last Night's Lifestyle

Raise Your HRV Tonight

  • • Consistent sleep schedule — HRV rises on nights after good rest
  • • Slow nasal breathing (6 breaths/min) boosts vagal tone within minutes
  • • Alcohol can cut next-day HRV by 10–20% — even one drink
  • • 150+ min/week of Zone 2 cardio raises long-term HRV

Don't know your training zones? Zone 2 Calculator →

What Is HRV & Why It Matters

Heart Rate Variability measures the millisecond variation between consecutive heartbeats. Unlike your heart rate (beats per minute), HRV reflects the balance between your sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) nervous systems. A higher HRV means your autonomic nervous system is more flexible — it can ramp up for stress, then calm down efficiently.

Elite athletes, healthy young adults, and people with low chronic stress consistently show higher HRV. Because HRV tracks recovery and stress, wearables like WHOOP, Oura, Garmin, and Apple Watch all report it — making it one of the most practical daily readiness signals available.

rMSSD vs SDNN — Which Metric Does Your Device Use?

DeviceMetricWhat It Measures
Oura / WHOOP / GarminrMSSDShort-term parasympathetic activity
Apple Watch / Clinical ECGSDNNOverall autonomic variability (both branches)

SDNN values are typically ~1.7× higher than rMSSD for the same person, so this calculator converts SDNN to an rMSSD equivalent (rMSSD ≈ 0.6 × SDNN) before comparing against rMSSD norms. Never compare your Apple Watch SDNN directly to rMSSD-based charts — you'll think your HRV is far higher than it is. Always select the correct metric.

HRV Normative Ranges by Age (rMSSD)

Nunan et al. (2010) meta-analysis — population ranges
AgeTypical Range (ms)Population Median
18–2535–85 ms55 ms
26–3532–78 ms50 ms
36–4527–65 ms42 ms
46–5521–52 ms33 ms
56–6517–42 ms26 ms
65+13–34 ms21 ms

More important than your absolute number is your personal 30-day trend — a sudden sustained drop below your baseline is the key warning signal, even if your value is still "in range."

How to Improve Your HRV

The most evidence-based HRV improvers, ranked by impact:

  • Consistent sleep schedule — going to bed at the same time every night may matter more than total hours.
  • Zone 2 cardio (60–70% max HR) 3–5×/week — the most reliable structural HRV improver over 8–12 weeks.
  • Slow paced breathing (5–6 breaths/min, 10 min/day) — directly boosts parasympathetic tone within a session.
  • Cold exposure — brief cold showers activate vagal tone.
  • Minimize alcohol, especially within 3 hours of sleep — even 1–2 drinks can drop next-day HRV 10–20%.

Frequently Asked Questions

What is a good HRV score?
HRV is highly individual — focus on your own 30-day trend rather than population comparisons. A 30yo male median is ~50ms rMSSD. Typical ranges: 18-25yo: 35-85ms; 26-35yo: 32-78ms; 36-45yo: 27-65ms; 46-55yo: 21-52ms; 56-65yo: 17-42ms; 65+: 13-34ms. A sudden sustained drop below your baseline is more meaningful than your absolute number.
rMSSD vs SDNN — which does my device use?
Oura, WHOOP, Garmin, and most Android wearables report rMSSD. Apple Watch reports SDNN. They measure different things — SDNN ≈ rMSSD ÷ 0.6 roughly. Never compare your Apple Watch SDNN directly to rMSSD-based charts — you'll think your HRV is much higher than it is. Always select the correct metric in this calculator.
What lifestyle factors hurt HRV most?
The biggest suppressors: (1) Alcohol — even 1-2 drinks can drop next-day HRV 10-20%. (2) Poor sleep — both duration and consistency matter. (3) Psychological stress — directly activates sympathetic nervous system. (4) Overtraining — too much intensity without recovery. (5) Illness — HRV often drops days before you feel symptoms. Evening alcohol is especially damaging as it disrupts the REM sleep stage when most HRV recovery happens.
How can I improve my HRV?
Best evidence-based methods: (1) Zone 2 cardio 3-5×/week — most reliable long-term HRV improver. (2) Resonance frequency breathing (5-6 breaths/min) — boosts parasympathetic tone within minutes. (3) Consistent sleep schedule — same bedtime matters as much as total hours. (4) Cold exposure — brief cold showers activate vagal tone. (5) Eliminate alcohol, especially within 3 hours of sleep. Results typically visible in 8-12 weeks.
Should I train or rest when HRV is low?
If your HRV is significantly below your personal 30-day baseline (red zone, <80%), prioritize rest and easy movement. Yellow zone (80-94%): consider low-intensity only. Green zone (≥95%): you're well-recovered and can train hard. Your relative baseline comparison is far more useful than comparing against population norms.
Why does my HRV vary so much day to day?
HRV is exquisitely sensitive to late alcohol intake, a poor night's sleep, psychological stress, a hard workout the day before, travel across time zones, even a single late meal. This day-to-day noise is normal — which is why WHOOP, Oura, and Garmin all use 30-day rolling averages rather than single readings. Interpret individual readings with context: what did you do the night before?

Also Try These Free Calculators

Zone 2 Heart Rate Calculator

Zone 2 training is the #1 way to structurally improve HRV.

VO2 Max Calculator

VO2 max and HRV are both key longevity markers.

Grip Strength Calculator

Another key longevity metric — check your percentile.

Biological Age Calculator

Combine HRV trends with your overall biological age score.