Amazfit Accuracy: Two Recovery Scores That Mostly Overlap
Runs two separate recovery-adjacent scores under different names, and has real peer-reviewed AFib detection accuracy behind its ECG feature.
Amazfit (made by Zepp Health) covers the full metric set at a lower price point than most brands compared here, built on its own BioTracker sensor and Zepp app ecosystem. Below is what published research and Amazfit's own documentation say about each metric it tracks, including a naming overlap worth knowing about before comparing scores day to day.
How Does Amazfit Measure HRV?
Amazfit measures HRV during sleep using RMSSD via its BioTracker PPG sensor (BioTracker 6.0 on current-generation devices), reporting how the body's autonomic nervous system responds to stress and relaxation.
What Amazfit calls it
"HRV," tracked overnight and fed into both the Readiness Score and BioCharge, Amazfit's two separate recovery-adjacent features.
KnowYourPrime Evidence Registry: Finding KYP-ER-0003: Wearable HRV Accuracy Against ECG.
How Does Amazfit Measure Resting Heart Rate?
Amazfit tracks resting heart rate overnight via the BioTracker sensor, feeding it into both PAI (its heart-rate-based activity score) and the Readiness Score.
What Amazfit calls it
"Resting Heart Rate," the same label as every other brand here, measured overnight during sleep.
How Does Amazfit Track Sleep?
Amazfit detects sleep onset by watching for heart rate dropping below the normal waking range alongside reduced movement, then tracks heart rate variability, movement patterns, and blood oxygen through the night to build a sleep profile.
What Amazfit calls it
Sleep tracking feeds directly into the Readiness Score the following morning rather than standing alone as its own separately-branded score in the same way Oura's or Garmin's Sleep Score does.
Worth knowing
In a sleep lab, raw movement data from a Huami Arc (Huami makes Amazfit) matched polysomnography minute by minute 90.3 percent of the time, catching 95.5 percent of sleep but only 55.6 percent of wake, in 21 sleep-clinic patients. The researchers scored that data with a standard research algorithm, not Amazfit's own sleep tracking, so it tests the sensor, not the sleep stages the app reports. A clinical-grade actigraph worn alongside scored about the same. Cheung et al., PLOS ONE, 2020.
KnowYourPrime Evidence Registry: Finding KYP-ER-0007: Wearable Sleep Tracking Accuracy Against a Sleep Lab.
What Does Amazfit's Readiness Score Measure?
Readiness Score is generated each morning from sleep resting heart rate, sleep HRV, breathing quality, and body temperature, a sleep-anchored recovery assessment that also feeds Zepp Coach's personalized training recommendations.
What Amazfit calls it
"Readiness Score." This is a distinct feature from BioCharge below, generated once per morning from overnight data specifically, rather than updating continuously through the day.
Worth knowing
A real peer-reviewed evaluation found composite recovery scores across brands are not methodologically equivalent to each other, despite similar-sounding names and overlapping inputs. No independent validation of Amazfit's Readiness Score specifically was found during research for this page.
KnowYourPrime Evidence Registry: Finding KYP-ER-0005: Readiness and Recovery Score Validity.
What Is BioCharge, and How Is It Different From Readiness Score?
BioCharge is a continuous, all-day energy score, 0-100, that peaks after a full night's sleep and depletes through the day as exercise, work, and stress accumulate, Amazfit's answer to Garmin's Body Battery.
What Amazfit calls it
"BioCharge." It draws on largely the same inputs as Readiness Score, sleep, HRV, resting heart rate, and stress, but updates continuously through the day rather than once each morning, the real functional difference between the two features despite the overlapping data behind them.
Worth knowing
An independent analysis of the BioCharge algorithm noted it doesn't add new physiological information beyond metrics already directly measurable elsewhere in the app, sleep duration, HRV, and resting heart rate, it's a weighted combination rather than a separately-sensed signal. The same underlying-metrics critique applies to most composite recovery scores across brands, not uniquely to Amazfit.
KnowYourPrime Evidence Registry: Finding KYP-ER-0005: Readiness and Recovery Score Validity.
How Accurate Is Amazfit's ECG?
Amazfit's ECG-capable models record a single-lead ECG on demand. In three studies of Amazfit-made hardware, the device's own ECG algorithm caught atrial fibrillation 87 to 94 percent of the time, and how often it was right about a normal rhythm ranged from 67 to 100 percent depending on the setting. A fourth study had trained technicians read the traces instead.
The four studies
Amazfit Health Band 1S, 401 people, about a third with AFib. The band's ECG algorithm: 87.33 percent sensitivity, 99.20 percent specificity. Its pulse sensor (PPG): 88.00 and 96.41 percent. When physicians read the same band ECG traces instead of the algorithm: 96.67 and 98.01 percent. Chen et al., Heart Rhythm, 2020 [author affiliations include Huami (Zepp Health, maker of Amazfit)]. Some of the authors are affiliated with Huami, which makes Amazfit.
Amazfit smartwatch against a 7-day Holter, 72 people with AFib. For episodes longer than 5 minutes, the PPG algorithm: 100 percent sensitivity, 83.7 percent specificity. The ECG algorithm: 89.7 and 67.4 percent. AFib burden tracked the Holter closely (agreement 0.976 for PPG, 0.927 for ECG). The authors name false positives as the weak point, and one author is medical director at Huami, which makes Amazfit. Pan et al., Digital Health, 2025 [author affiliations include Huami (Zepp Health, maker of Amazfit); funding listed from Huami (Zepp Health, maker of Amazfit)].
Huami wristband ECG recorder, 114 outpatients, 53 with AFib. Lying down: 88.68 percent sensitivity, 100 percent specificity. Upright: 94.34 and 100 percent. Fu and Li, BMC Cardiovascular Disorders, 2021.
AMAZFIT ECG recorder read by technicians, 291 adults averaging 78. Two trained technicians, not the algorithm, read the recordings, nearly all from the chest lead: 93.28 percent sensitivity and 95.35 percent specificity for AFib, 84.00 percent sensitivity for premature atrial beats, 89.29 percent for premature ventricular beats, and 32.14 percent for first-degree heart block. Zhang et al., Frontiers in Medicine, 2021.
Correction, 2026-10-09
This section previously credited 93.28 percent sensitivity and 95.35 percent specificity to Amazfit's AFib detection. In that study, trained technicians read recordings from an AMAZFIT ECG recorder, mostly taken at the chest, in 291 older adults; it did not test the watch's automatic detection. The section now reports all four studies and which kind of reading each one tested.
Does Amazfit Measure Pulse Rate or Heart Rate?
Pulse rate. An optical sensor at the wrist reads the pressure wave arriving in the blood vessels under the skin, which is not the same measurement as the heart's electrical contraction, even though the two numbers usually agree.
Why the distinction is real and not pedantry
Heart rate is how often the heart contracts, and the direct way to measure it is electrically, which is what an ECG does. Pulse rate is how often a pressure wave reaches the wrist, and the direct way to measure that is optically, which is what every wrist and ring sensor does. In a steady, regular rhythm the two match closely enough that the distinction does not matter to a reader. They separate when a contraction is too weak to push a wave to the periphery, which is what happens in an irregular rhythm: the heart beats and the wrist does not feel it. That is why Amazfit's ECG feature exists as a separate thing from its optical heart rate, rather than being the same measurement twice.
What published research found
Close at rest, drifts apart with exertionA systematic review retrieving 308 articles and including 18 found that the correlation between ECG-derived heart rate variability and the variability a wearable reports ranged from very good to excellent at rest, and declined progressively as exercise intensity increased. The same review is an anchor on KnowYourPrime's HRV desk. One limit in it matters for a reader holding an optical device: only two of the eighteen studies used the photoplethysmography and pulse-rate-variability combination that a wrist sensor actually uses, the other sixteen being ECG-based wearables, so the evidence specific to optical measurement is thinner than that review alone suggests. A dedicated synthesis of exactly that comparison now exists and is the better place to look as it matures: a systematic review and meta-analysis evaluating PPG-derived pulse rate variability against ECG-derived heart rate variability in healthy, non-clinical populations, focused on RMSSD, which is the measure consumer devices report. It was added to KnowYourPrime’s HRV desk on 2026-10-07.
Georgiou et al., Folia Medica, 2019 (doi:10.2478/folmed-2018-0012), anchor study on KnowYourPrime's HRV deskCan Amazfit Support a Corporate Wellness or Preventive Care Program?
Nothing published supports that use. Readiness Score and BioCharge are proprietary composites whose weighting Amazfit does not disclose, and no independent study has tested either against a workplace or preventive-care outcome.
What the evidence underneath does and does not support
There is evidence for the signal these products are built on, and it is not the same thing as evidence for the product. KnowYourPrime's HRV desk rates whether higher occupational stress is associated with lower heart rate variability as Emerging, on six studies. Two reviews support it: across 10 studies of workers, nine of them cross-sectional, higher job stress went with lower HRV (Industrial Health, 2019), and in seven small studies of doctors, HRV was lower in their own stress periods than in recovery periods (Occupational Medicine, 2026). The qualification is what happens inside a working day: when 101 teachers rated their job demands six times a day while wearing an ECG, the demands raised exhaustion and did not lower state HRV (Anxiety, Stress, and Coping, 2021). So HRV separated stressful periods from recovery, and did not follow how demanding the day was from hour to hour.
Correction, 2026-10-25
This section previously said the link between work stress and HRV did not hold within one person's day. Doctors' HRV was lower in their own stress periods than in recovery periods; the null result is narrower, job demands rated through a teacher's school day.
That distinction decides whether a workplace deployment makes sense. A group-level association supports a statement about populations. It does not support a prediction about the person wearing the watch on Tuesday, and a preventive-care program is built entirely out of predictions about individual people. KnowYourPrime's recovery desk rates whether consumer readiness and recovery scores measure what they claim as Uncertain, on five studies, and that applies to every vendor in the category rather than to this one.
What randomized trials of workplace wellness programs found, including the trials that gave employees a tracker, is set out in whether workplace wellness programs and wearables work.
KnowYourPrime Evidence Registry: Finding KYP-ER-0006: Work Stress and HRV; Finding KYP-ER-0005: Readiness and Recovery Score Validity.
How Does Amazfit Measure Blood Oxygen?
Amazfit tracks SpO2 via the BioTracker sensor, available both on-demand and as part of continuous overnight monitoring.
Worth knowing
No Amazfit-specific independent SpO2 accuracy study was found during research for this page. General PPG-based pulse oximetry research, including documented accuracy differences by skin pigmentation, applies broadly but wasn't tested against Amazfit by name.
KnowYourPrime Evidence Registry: Finding KYP-ER-0001: Smartwatch Blood Oxygen (SpO2) Accuracy Against Arterial Blood (SaO2); Finding KYP-ER-0002: Pulse Oximeter Accuracy and Skin Tone.
What Amazfit Doesn't Do
One real, worth-knowing overlap rather than an absence.
No single, unambiguous recovery number
Readiness Score and BioCharge both draw on the same core inputs and can read differently on the same morning, worth understanding before treating either as a single definitive daily readiness figure the way Oura's or Whoop's single score is designed to be read.
If a full metric set at a lower price point, with a validated ECG feature, matters more than an established multi-year research base, Amazfit is a real contender. Its two overlapping recovery-adjacent scores are worth understanding clearly before relying on either one the way a reader might rely on Oura's single Readiness number.
KnowYourPrime Evidence Registry: Finding KYP-ER-0004: Chest Strap HRV Accuracy Against ECG