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HRV Deviation Calculator
Morning HRV readiness check — compare today's HRV against your 7-day baseline to guide training decisions.
⚠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.
HRV deviation reference
| Deviation | Interpretation | Action |
|---|
| > +10% | Elevated HRV | Train hard |
| +5 to +10% | Good readiness | As planned |
| −5 to +5% | Normal baseline | As planned |
| −5 to −10% | Below baseline | Reduce intensity |
| < −10% | Suppressed HRV | Rest or easy only |
Source: Plews DJ et al. (2013). Heart rate variability in elite triathletes. International Journal of Sports Physiology and Performance.
Frequently asked questions
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.
What is a good HRV score?
There is no universal "good" score — HRV is highly individual. Values typically range from 20 to 100ms (RMSSD) depending on age, fitness level, and device. A sedentary 50-year-old might average 25ms; an elite 25-year-old endurance athlete might average 90ms. What matters is YOUR personal baseline and how much you deviate from it on any given day.
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 24–48 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 3–5+ 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 12–24 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.