Garmin’s stress level is not a mood reading. It is a 0 to 100 score derived from heart rate variability (HRV) while you are inactive, so anything that keeps your heart rate up or your HRV down while you sit still can push it high: illness, alcohol, poor sleep, caffeine, a hot room, or genuine pressure. A high number means “your body looks under load”, not “you are anxious”.
The scale
Garmin’s owner’s manuals give four bands:
| Score | Garmin’s label |
|---|---|
| 0 to 25 | Resting state |
| 26 to 50 | Low stress |
| 51 to 75 | Medium stress |
| 76 to 100 | High stress |
The manual’s description is short: the watch analyses your heart rate variability while you are inactive to work out your overall stress, and training, physical activity, sleep, nutrition and general life stress all affect the level. Garmin says that for best results you should wear the device while sleeping. Garmin’s blog adds that its watches use Firstbeat Analytics (a company Garmin bought in 2020) to interpret the timing of heartbeats, and that stress readings are summarised over three-minute windows.
That is nearly everything Garmin says. It does not publish the formula, how your personal baseline is set, or how long it takes to adapt. So claims about exactly how the number is built should be read with suspicion.
Why HRV works as a stress proxy
HRV is the small variation in the gap between heartbeats. Garmin’s explanation is the standard one: when the sympathetic (“fight or flight”) side of the nervous system is more active, heart rate tends to rise and HRV to fall, and when the parasympathetic (“rest and digest”) side takes over, heart rate falls and HRV rises. Garmin’s blog on illness makes the same point, noting that stress and exercise may raise heart rate and drop HRV, and that a fever can start an immune response that stresses the body, with a small rise in body temperature pushing heart rate up by roughly 7 beats per minute.
The catch is that the watch cannot tell why your nervous system is in that state. A hard argument, a half-finished cold, a double espresso and a hangover can all look identical from a wrist.
Why yours might read high
Work through these in order of how often they explain a persistently high reading.
- You are carrying a recovery debt. After hard training or a run of short nights, your resting HRV is lower than normal and the stress score follows. This is the watch working as intended.
- Alcohol or a late meal. Both tend to raise overnight heart rate and lower HRV for many people, so the following day’s stress graph starts high. Try two weeks without either in the evening and compare.
- Illness coming or going. Garmin’s own blog links infections with lower HRV and higher heart rate. If your stress has been high for a few days and you feel slightly off, that is worth noticing before you train.
- Caffeine, nicotine and heat. Anything that lifts resting heart rate while you are still can push the reading up.
- Fit and fine, but the baseline is off. Your personal baseline is not published. If you changed training, medication or sleep patterns recently, the baseline may be catching up.
- Sensor noise. A loose watch or a poor optical reading gives bad HRV. Wearing it snugly is the cheap fix.
- Not wearing it in bed. Garmin says wearing the device while sleeping gives the best results. Without overnight data, the all-day picture is thinner.
None of these needs a lifestyle overhaul. Check for patterns first: look at your all-day stress graph in Garmin Connect and find when the high stretches begin. If the stress is high at 3 am, the cause is not your email.
What a “good” number is
There is no universal good number, only your own range. A person with a stress average in the 30s on most days and a run of 60s while ill has learned something useful. A person who averages 50 every day may have a genuinely demanding life, or a watch whose baseline is simply set differently. Compare your readings with your own last month, not with a friend’s. Look at the shape of the day as well as the average: a graph that dips into the resting band overnight and climbs through the working day is normal, and a graph that never dips is the one worth investigating, usually through sleep, alcohol or illness. If it never dips and you wear the watch to bed, check that it is recording sleep properly in the first place.
If your score is at the top end for weeks, you feel run down, and your resting heart rate is above your usual, take that seriously. Persistent symptoms such as a racing heart at rest, chest pain, dizziness or breathlessness are a reason to see a doctor, not to adjust a setting.
A second view from a different method
Pulse, a free app you host yourself, offers a Stress Monitor built from Google Health heart rate rather than HRV. It looks only at still minutes (no steps in that minute or the two either side, and not during sleep or workouts), measures how far heart rate sits above your own calm level, and maps that onto a 0 to 3 scale (how Stress Monitor works). It needs four days to set a baseline, reads heart rate alone, and is tested with the Fitbit Air only. Like Garmin’s, it cannot say how you feel, and caffeine, heat and illness raise it too. Two different methods that agree are slightly more convincing than one; two that disagree mostly tell you the measurement is rough.
What is not known
Garmin does not publish the stress algorithm, so how HRV is converted to 0 to 100, how the baseline adapts, and how much each input counts are all unknown outside the company. The manual wording used here is from older vivoactive and Venu manuals; newer devices may describe it differently, so check the manual for your model.
Fitbit took a different route on stress: it replaced its numeric score with labels, covered in Fitbit Resilience replaced the stress score.