Device research record

Apple Watch Series 6

19 Validation results
3 Comparisons
5 Articles

Signals and sensors

From the device record. Fields the source does not state are left out.

Maker: Apple
Form factor: Wrist
Series: Series 6
Family: Apple Watch
Signals recorded: PPG, Accelerometer, ECG
Also called: Apple Watch S6, Watch Series 6

What published studies show

Results quoted from 9 published validation studies, each against a clinical reference. A result applies to the model and protocol tested, not to every model the brand sells. From the wearable accuracy database (v1.0.0).

Heart rate at rest1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6R-R intervals and BPM at rest	1.15%Mean absolute percentage error	ECG	n = 78, Lab: rest, talking, movie, before/after walking	Bonneval et al. (2025)Independent

Apple Watch Series 61.15%
Mean absolute percentage error, R-R intervals and BPM at rest · vs ECG · n = 78, Lab: rest, talking, movie, before/after walking
Bonneval et al. (2025) Independent

Heart rate accuracy across devices →

Heart rate during exercise2 studies

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	High agreement in squat, deadlift, cable row (rho > 0.832)Study finding (no single number)	ECG chest strap (Polar H7/H10)	n = 29, Resistance exercise (5 exercises)	Støve et al. (2022)Funding not reported
Apple Watch Series 6	< 5% in all 5 activitiesCoefficient of variation	ECG chest strap (Polar H7/H10)	n = 60, Sitting, walking, running, resistance, cycling	Hajj-Boutros et al. (2023)Funding not reported

Apple Watch Series 6High agreement in squat, deadlift, cable row (rho > 0.832)
Study finding (no single number) · vs ECG chest strap (Polar H7/H10) · n = 29, Resistance exercise (5 exercises)
Støve et al. (2022) Funding not reported
Apple Watch Series 6< 5% in all 5 activities
Coefficient of variation · vs ECG chest strap (Polar H7/H10) · n = 60, Sitting, walking, running, resistance, cycling
Hajj-Boutros et al. (2023) Funding not reported

Heart rate accuracy across devices →

Overnight heart rate1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	ICC 0.96Intraclass correlation	ECG	n = 53, Overnight, sleep laboratory	Miller et al. (2022)Other maker funded
Apple Watch Series 6	1.5 bpm (absolute bias)Mean absolute error	ECG	n = 53, Overnight, sleep laboratory	Miller et al. (2022)Other maker funded

Apple Watch Series 6ICC 0.96
Intraclass correlation · vs ECG · n = 53, Overnight, sleep laboratory
Miller et al. (2022) Other maker funded
Apple Watch Series 61.5 bpm (absolute bias)
Mean absolute error · vs ECG · n = 53, Overnight, sleep laboratory
Miller et al. (2022) Other maker funded

Heart rate accuracy across devices →

HRV (RMSSD)1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	ICC 0.67Intraclass correlation	ECG	n = 53, Overnight, sleep laboratory	Miller et al. (2022)Other maker funded
Apple Watch Series 6	22.5 ms (absolute bias)Mean absolute error (absolute bias)	ECG	n = 53, Overnight, sleep laboratory	Miller et al. (2022)Other maker funded

Apple Watch Series 6ICC 0.67
Intraclass correlation · vs ECG · n = 53, Overnight, sleep laboratory
Miller et al. (2022) Other maker funded
Apple Watch Series 622.5 ms (absolute bias)
Mean absolute error (absolute bias) · vs ECG · n = 53, Overnight, sleep laboratory
Miller et al. (2022) Other maker funded

HRV accuracy across devices →

Sleep stages (4-stage)1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	53%Epoch-by-epoch agreement	Polysomnography (PSG)	n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together	Miller et al. (2022)Other maker funded
Apple Watch Series 6	κ = 0.20Cohen's kappa	Polysomnography (PSG)	n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together	Miller et al. (2022)Other maker funded

Apple Watch Series 653%
Epoch-by-epoch agreement · vs Polysomnography (PSG) · n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together
Miller et al. (2022) Other maker funded
Apple Watch Series 6κ = 0.20
Cohen's kappa · vs Polysomnography (PSG) · n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together
Miller et al. (2022) Other maker funded

Sleep accuracy across devices →

Sleep vs wake (2-stage)1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	88%Epoch-by-epoch agreement	Polysomnography (PSG)	n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together	Miller et al. (2022)Other maker funded
Apple Watch Series 6	κ = 0.30Cohen's kappa	Polysomnography (PSG)	n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together	Miller et al. (2022)Other maker funded

Apple Watch Series 688%
Epoch-by-epoch agreement · vs Polysomnography (PSG) · n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together
Miller et al. (2022) Other maker funded
Apple Watch Series 6κ = 0.30
Cohen's kappa · vs Polysomnography (PSG) · n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together
Miller et al. (2022) Other maker funded

Sleep accuracy across devices →

Blood oxygen (SpO2)3 studies

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	r = 0.89Pearson correlation	Medical-grade pulse oximeter	n = 265, Spot readings	Spaccarotella et al. (2022)Independent
Apple Watch Series 6	−0.23 (LoA −3.49 to 3.04)Mean bias (signed)	Medical-grade pulse oximeter	n = 265, Spot readings	Spaccarotella et al. (2022)Independent
Apple Watch Series 6	Not yet up to the medical standard of pulse oximetryStudy finding (no single number)	Medical-grade pulse oximeter	n = 508, Congenital heart disease clinic	Pätz et al. (2023)Funding not reported
Apple Watch Series 6	0.46% vs ABG (LoA −5.91 to 5.00)Mean bias (signed)	Arterial blood gas (SaO2)	n = 167, Emergency department, COPD exacerbation	Arslan et al. (2024)Funding not reported

Apple Watch Series 6r = 0.89
Pearson correlation · vs Medical-grade pulse oximeter · n = 265, Spot readings
Spaccarotella et al. (2022) Independent
Apple Watch Series 6−0.23 (LoA −3.49 to 3.04)
Mean bias (signed) · vs Medical-grade pulse oximeter · n = 265, Spot readings
Spaccarotella et al. (2022) Independent
Apple Watch Series 6Not yet up to the medical standard of pulse oximetry
Study finding (no single number) · vs Medical-grade pulse oximeter · n = 508, Congenital heart disease clinic
Pätz et al. (2023) Funding not reported
Apple Watch Series 60.46% vs ABG (LoA −5.91 to 5.00)
Mean bias (signed) · vs Arterial blood gas (SaO2) · n = 167, Emergency department, COPD exacerbation
Arslan et al. (2024) Funding not reported

SpO2 accuracy across devices →

Atrial fibrillation detection1 study

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6smartwatch ECG app, inconclusive tracings counted	85% (spec 75%)Sensitivity	12-lead ECG	n = 201, Tertiary cardiology service, single-lead ECG algorithms	Mannhart et al. (2023)Funding not reported
Apple Watch Series 6smartwatch ECG app, inconclusive tracings counted	75%Specificity	12-lead ECG	n = 201, Tertiary cardiology service, single-lead ECG algorithms	Mannhart et al. (2023)Funding not reported

Apple Watch Series 685% (spec 75%)
Sensitivity, smartwatch ECG app, inconclusive tracings counted · vs 12-lead ECG · n = 201, Tertiary cardiology service, single-lead ECG algorithms
Mannhart et al. (2023) Funding not reported
Apple Watch Series 675%
Specificity, smartwatch ECG app, inconclusive tracings counted · vs 12-lead ECG · n = 201, Tertiary cardiology service, single-lead ECG algorithms
Mannhart et al. (2023) Funding not reported

AFib accuracy across devices →

Energy expenditure (calories)2 studies

Device tested	Result	Reference	Sample	Study
Apple Watch Series 6	14.68–24.85% (poor in all activities)Coefficient of variation	Indirect calorimetry	n = 60, Sitting, walking, running, resistance, cycling	Hajj-Boutros et al. (2023)Funding not reported
Apple Watch Series 6walking	19.8% walk / 24.4% runMean absolute percentage error	Indirect calorimetry	n = 20, Outdoor 2-km walk (6 km/h) and run (10 km/h)	Le et al. (2022)Independent

Apple Watch Series 614.68–24.85% (poor in all activities)
Coefficient of variation · vs Indirect calorimetry · n = 60, Sitting, walking, running, resistance, cycling
Hajj-Boutros et al. (2023) Funding not reported
Apple Watch Series 619.8% walk / 24.4% run
Mean absolute percentage error, walking · vs Indirect calorimetry · n = 20, Outdoor 2-km walk (6 km/h) and run (10 km/h)
Le et al. (2022) Independent

Calories accuracy across devices →

Comparisons

Head-to-head pages that name Apple Watch Series 6 come first, then other comparisons for the brand.

Articles that mention Apple Watch Series 6

Other versions

Apple Watch Apple Watch Series 7 Apple Watch Series 8 Apple Watch Series 9+Apple Watch Ultra

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