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HRV Calculator: Training Readiness from HRV Deviation
Morning HRV readiness check. Compare today's HRV against your 7-day baseline to guide training decisions.
What is a good HRV?
HRV varies widely by age, fitness, and individual baseline. Average resting HRV (RMSSD) runs about 55 to 80 ms for age 18 to 25, 35 to 55 ms for age 35 to 45, 15 to 30 ms for age 65+, on the same grid as the table further down. Those bands are this site's convention rather than a published norm table. Individual baseline matters more than population averages, track YOUR trend over weeks, not a single reading. A 10% drop from your 7-day average suggests your body needs recovery, regardless of the number. Use the calculator below to check your deviation from baseline.
⚠For reference only. HRV varies with measurement method, time of day, and individual baseline. Single-day readings are less meaningful than trends. Use a consistent morning measurement protocol.
-8.1%
HRV below baseline
Today: 68 ms · Baseline: 74 ms
HRV slightly suppressed. Consider a lighter session, Zone 2 only, or extra recovery work today.
Low HRV? Your body needs rest. Try an active recovery session instead of training.
Normal HRV Ranges by Age (RMSSD)
Use these population averages as orientation only, your personal baseline is what matters for daily decisions.
| Age | Low | Average | Good | Elite |
|---|
| 18 to 25 | <40 ms | 55 to 80 ms | 80 to 110 ms | 100 to 140+ ms |
| 25 to 35 | <35 ms | 45 to 70 ms | 70 to 100 ms | 90 to 130+ ms |
| 35 to 45 | <25 ms | 35 to 55 ms | 55 to 80 ms | 75 to 110+ ms |
| 45 to 55 | <20 ms | 25 to 45 ms | 45 to 70 ms | 60 to 90+ ms |
| 55 to 65 | <15 ms | 20 to 35 ms | 35 to 55 ms | 50 to 75+ ms |
| 65+ | <12 ms | 15 to 30 ms | 30 to 45 ms | 40 to 60+ ms |
Values are for morning resting RMSSD measured with chest strap or validated optical sensor. Finger-based and wrist-based sensors may give different values. Individual baseline matters more than population averages, track YOUR trend over weeks, not a single reading.
HRV Deviation: What Your Score Means
The deviation from your 7-day baseline maps to a readiness zone and a training recommendation:
| Deviation | Status | Training |
|---|
| > +10% | Above baseline | Train hard, intensity OK |
| -5 to +10% | Normal range | Train as planned |
| -10 to -5% | Slightly low | Train moderate |
| -15 to -10% | Below baseline | Easy / active recovery |
| < -15% | Significantly low | Rest day recommended |
Source for the method, comparing a reading against your own rolling baseline: Plews DJ et al. (2013), Heart rate variability in elite triathletes, International Journal of Sports Physiology and Performance. The age table is a separate claim and has no source: those bands are this site’s convention, and a study of elite triathletes cannot be the source of a population norm for a sixty five year old. Published population RMSSD figures live in Shaffer and Ginsberg (2017) and the 1996 Task Force report, neither of which is quoted here.
What Is HRV and Why Does It Matter for Training?
Heart Rate Variability (HRV) measures the variation in time between heartbeats. Higher HRV generally indicates better cardiovascular fitness and recovery, your nervous system has more capacity to adapt. Lower HRV suggests stress, fatigue, or incomplete recovery. For athletes, morning HRV is the most reliable daily readiness indicator because it reflects your autonomic nervous system state before external stressors (work, caffeine, exercise) affect it. A single HRV reading means little, the TREND compared to your personal baseline is what matters.
How to Measure HRV Correctly
For accurate HRV tracking: (1) Measure every morning, immediately after waking, before getting out of bed. (2) Use the same device every time, chest strap (Polar H10, Garmin HRM-Pro) is gold standard, optical sensors (Apple Watch, Whoop, Oura) are acceptable. (3) Measure for at least 60 seconds (ideally 2 to 3 minutes). (4) Breathe naturally, don't try to control breathing. (5) Same position every time (lying down). (6) Record the value in your app. The calculator above compares today's reading to your 7-day rolling average, this is the method used by elite sport scientists (Plews et al., 2013).
HRV vs Resting Heart Rate: Which Is Better?
Both are useful but HRV is more sensitive. Resting heart rate changes only when you're significantly fatigued or overtrained, it's a lagging indicator. HRV detects subtle shifts in autonomic balance 1 to 2 days before you "feel" tired. Think of resting HR as a smoke alarm (fires when there's already a fire) and HRV as a smoke detector (detects early signs). The calculator above optionally includes resting HR to give a combined readiness assessment.
What Affects HRV?
Factors that lower HRV: poor sleep (biggest factor), alcohol (even 1 to 2 drinks), heavy training the day before, psychological stress, illness/infection (HRV drops 24 to 48h before symptoms), dehydration, travel/jet lag. Factors that raise HRV: good sleep (7 to 9h), consistent training with adequate recovery, meditation/breathwork, aerobic fitness improvements over months. A single low reading isn't alarming, look for patterns over 3 to 5 days.
Frequently asked questions
What is a good HRV score?
It depends on age and fitness. Average RMSSD runs about 55 to 80 ms for age 18 to 25, 35 to 55 ms for age 35 to 45, 15 to 30 ms for age 65+ on the grid this page uses. Elite athletes often have HRV above 100 ms. Those bands are this site’s convention, not a published norm table: Plews et al. 2013 supports the method here, comparing a reading with your own rolling baseline, but it studied elite triathletes and cannot be the source of a population norm. Individual baseline matters more than population averages, track YOUR trend over weeks, not a single reading.
Is higher HRV always better?
Generally yes, higher HRV indicates better parasympathetic tone and recovery capacity. However, very high HRV with no training stimulus can indicate detraining. And a sudden spike in HRV after hard training can indicate parasympathetic rebound (the body overcorrecting), not necessarily readiness.
How often should I measure HRV?
Every morning for the most useful data. The 7-day rolling average needs at least 5 to 7 data points to be meaningful. Missing a day is fine. Missing 3+ days breaks the trend and reduces accuracy.
Can I use Apple Watch, Garmin or Whoop for HRV?
Yes, all three provide usable HRV data. Apple Watch measures overnight HRV automatically. Garmin measures morning HRV (Body Battery). Whoop measures continuously overnight. Each uses slightly different algorithms, so don’t compare numbers between devices. Pick one and stick with it.
What does HRV deviation mean?
HRV deviation = how much today’s reading differs from your 7-day average, expressed as a percentage. Formula: ((today - average) ÷ average) × 100. A deviation of -10% means today’s HRV is 10% below your recent average, suggesting incomplete recovery or stress. Use the seven days BEFORE today as the average and leave today out of it: if today is inside its own baseline it pulls the average toward itself and shrinks the deviation, which matters most on exactly the days a large swing is the signal you wanted to see.
What is HRV and why does it matter for athletes?
HRV (Heart Rate Variability) is the variation in time between consecutive heartbeats, measured in milliseconds. It reflects the balance between your sympathetic (stress) and parasympathetic (recovery) nervous systems. High HRV indicates good recovery and autonomic balance. For athletes, daily HRV monitoring tracks cumulative fatigue and readiness, helping to time hard sessions when the body is ready and avoid overtraining.
Why does my HRV vary so much day to day?
Single-day HRV readings have significant natural variation caused by circadian rhythm, measurement timing, hydration, sleep quality, mental stress, and caffeine. This is why a 7-day rolling average is used as the baseline: it smooths out this noise. A one-day drop from 70ms to 62ms is less meaningful than a 5-day trend from 70ms down to 58ms. Always look at trends, not single readings.
What does low HRV mean after a hard workout?
Acutely suppressed HRV in the 24 to 48 hours after a hard session is completely normal and expected. Intense training generates sympathetic nervous system activation and muscle damage, both of which temporarily suppress HRV. This is not a problem; it is a normal training response. Concern arises when HRV remains suppressed for 3 to 5+ days without recovering toward baseline, which may indicate accumulated fatigue or overtraining.
Should I skip training if my HRV is low?
Not necessarily skip, but modify. A deviation of -5% to -10% suggests a lighter session: Zone 2 cardio, technique work, or mobility. A deviation below -10% is a stronger signal to rest or do very light activity only. Always combine HRV with subjective feel: if both are poor, that is a clear rest day signal. If HRV is down but you feel fine, consider a moderate session and monitor the trend.
What is the best time of day to measure HRV?
First thing in the morning, before getting out of bed, after 5 minutes lying still. HRV naturally varies throughout the day due to circadian rhythm, posture changes, food, and activity. Morning measurements capture the most stable and reproducible baseline. Measurements taken at different times of day are not directly comparable and should not be averaged into the same baseline.
Does caffeine or alcohol affect HRV?
Yes, significantly. Alcohol suppresses HRV for 12 to 24 hours after consumption, even when you do not feel hungover. This is one of the most consistent and dramatic HRV effects. Caffeine has a modest short-term effect that clears within a few hours. For this reason, always measure HRV before coffee or tea, and note alcohol consumption in your training log alongside your HRV reading to avoid misinterpreting the suppression as training fatigue.