Amazfit: What the Research Says About Each Metric
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 independent 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.
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.
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.
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.
How Accurate Is Amazfit's ECG?
Amazfit's ECG-capable models detect atrial fibrillation, premature atrial contractions, and premature ventricular contractions via a single-lead on-demand reading.
Worth knowing
A peer-reviewed evaluation of Amazfit's AFib detection reported 93.28 percent sensitivity and 95.35 percent specificity, with significantly higher sensitivity and specificity for AFib, PACs, and PVCs compared to reference methods, a genuine, specific accuracy figure most brands in this comparison don't have published for their own ECG feature.
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.
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 genuinely 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.