Device comparisons
Oura Ring vs Apple Watch: Finger PPG vs Wrist PPG Accuracy
Oura is a ring built mainly for sleep and recovery; Apple Watch is a full smartwatch with ECG. Three studies tested both against polysomnography. In Miller 2022 (53 adults), Oura Gen 2 had higher sleep-stage agreement than Apple Watch Series 6 (61% vs 53%) while Apple Watch tracked overnight heart rate more closely (ICC 0.96 vs 0.85); overnight HRV agreement was similar (0.67 vs 0.63). In the independent Lee 2023 study, four-stage kappa was 0.35 for Oura Gen3 and 0.30 for Apple Watch Series 8. An Oura-funded study (Robbins 2024, 35 adults) reported stage sensitivity of 76.0–79.5% for Oura Gen3 and 50.5–86.1% for Apple Watch Series 8.
Published study results
| Metric | Apple Watch Series 10 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Sleep stagesEpoch agreement vs PSGMiller et al. 2022, n=53 | 53%κ 0.20 · Series 6 | 61%κ 0.43 · Oura Gen 2Closer in this study |
| Overnight heart rateICC vs ECGMiller et al. 2022, n=53 | 0.96Series 6Closer in this study | 0.85Oura Gen 2 |
| Sleep stagesFour-stage κ vs PSGLee et al. 2023 | 0.30Series 8 | 0.35Oura Gen3 |
Each row is one statistic from a study already cited on this page. The link names the sample size when this page already states it. This is not a new measurement.
Devices
Apple Watch Series 10, jet black aluminum with a black sport band: product photograph from Apple Newsroom, September 2024. Oura Ring 4 in silver: product photograph from Oura.
Quick answer
Oura has scored better for sleep stages and Apple Watch for overnight heart rate. In a 53-adult sleep-lab study, Oura Gen 2 matched polysomnography sleep stages in 61% of epochs versus 53% for Apple Watch Series 6, while Apple Watch tracked overnight heart rate more closely (ICC 0.96 vs 0.85). An independent study found four-stage kappa of 0.35 for Oura Gen3 and 0.30 for Apple Watch Series 8.
Sources: Miller et al. 2022, Sensors; Lee et al. 2023, JMIR mHealth uHealth
At a glance
Miller et al. 2022 tested six devices on 53 adults for one night (Oura Gen 2 and Apple Watch Series 6). Lee et al. 2023 is a separate polysomnography study of later models. Robbins et al. 2024 was funded by Oura and is not in this table.
| Specification | Apple Watch Series 10 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Sleep stagesEpoch agreement vs PSG | 53%κ 0.20 · Series 6 | 61%κ 0.43 · Oura Gen 2Closer in this study |
| Overnight heart rateICC vs ECG | 0.96Series 6Closer in this study | 0.85Oura Gen 2 |
| Sleep stagesFour-stage κ vs PSGDiffers | 0.30Series 8 | 0.35Oura Gen3 |
Primary rows only. The study tables further down list more results from the accuracy database.
Hardware specs
| Specification | Apple Watch Series 10 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Battery LifeDiffers | Up to 18 hours; 36 hours Low Power Mode | Up to 7 days (Gen3); typically 5–8 days (Ring 4) |
| Water ResistanceDiffers | 50 m (ISO 22810:2010) | 100 m |
| ECGDiffers | Yes | No |
Hardware only. Study results are not repeated in this table. Differs marks values that are not the same. An em dash means this page did not publish that figure.
Specs verified on October 17, 2026: Miller et al. 2022, Sensors (six devices vs PSG and ECG, n=53), Lee et al. 2023, JMIR mHealth uHealth (11 consumer sleep trackers vs PSG), Robbins et al. 2024, Sensors (Oura Gen3, Apple Watch S8, Fitbit Sense 2 vs PSG; Oura-funded), Gillinov et al. 2017, Med Sci Sports Exerc (exercise HR vs ECG, n=50), Stone et al. 2021, Front Sports Act Living (resting HRV), Apple Watch Series 10 technical specifications, Oura: Smart Sensing in Oura Ring 4, Oura Support: Oura Ring 4 battery life, Oura Support: general FAQs (battery, water resistance), Oura Support: previous Oura Ring generations, Oura Support: Oura Membership.
Pros and cons
Apple Watch Series 10
Pros
- Overnight HR ICC 0.96 vs ECG for Series 6 (Miller 2022)
- Exercise HR concordance 0.92 with ECG (Gillinov 2017)
- ECG app and irregular rhythm notifications
Cons
- Sleep-stage agreement 53% (κ 0.20) for Series 6 (Miller 2022)
- Up to 18 hours battery
Oura Ring (Gen3 / Ring 4)
Pros
- Sleep-stage agreement 61% (κ 0.43) for Gen 2 (Miller 2022)
- Battery up to 7 days (Gen3) or typically 5–8 days (Ring 4)
- Resting RMSSD within 6.84% of ECG (Stone 2021)
Cons
- No ECG
- Detailed metrics require an Oura membership
What published studies show
One table per metric. These rows come from the accuracy database and are not repeated as a second card list. From the wearable accuracy database (v1.0.0).
Heart rate at rest3 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 9 / Ultra 2 | 5.91% (MAE 3.73 bpm)Mean absolute percentage error | Polar H10 + Kubios HRV | n = 39, Serial morning measurements over 14 days, 316 readings | O'Grady et al. (2024)Independent |
| Apple Watch Series 6R-R intervals and BPM at rest | 1.15%Mean absolute percentage error | ECG | n = 78, Lab: rest, talking, movie, before/ | Bonneval et al. (2025)Independent |
| Oura Ring (Gen2) | r = 0.90Pearson correlation | Actiheart (ECG + accelerometer) | n = 21, Free-living, up to 7 days | Henriksen et al. (2022)Independent |
| Oura Ring (Gen2) | 3%Mean absolute percentage error | Actiheart (ECG + accelerometer) | n = 21, Free-living, up to 7 days | Henriksen et al. (2022)Independent |
Heart rate during exercise10 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/ | n = 29, Resistance exercise (5 exercises) | Støve et al. (2022)Funding not reported |
| Apple Watch SE | Significantly lower MAE than Polar Pacer Pro and Galaxy Watch 6Study finding (no single number) | ECG chest strap (Polar H7/ | n = 37, Low/ | Jeong et al. (2026)Independent |
| Apple Watch Series 8 | Skin pigmentation did not predict error (P = 0.62); 50% of missing data from dark-skin participantsStudy finding (no single number) | ECG chest strap (Polar H7/ | n = 28, Rest, cycling, recovery | Mulholland et al. (2026)Independent |
| Apple Watch Series 9 | Less accurate for darker skin pigmentationStudy finding (no single number) | ECG chest strap (Polar H7/ | n = 30, 10-min treadmill | Chase et al. (2024)Independent |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 4 | 0.9%–4.3% (range by intensity)Coefficient of variation | ECG chest strap (Polar H7/ | n = 25, Sitting, walking, running, sprints | Düking et al. (2020)Independent |
| Apple Watch Series 6 | < 5% in all 5 activitiesCoefficient of variation | ECG chest strap (Polar H7/ | n = 60, Sitting, walking, running, resistance, cycling | Hajj-Boutros et al. (2023)Funding not reported |
4 more results in the database. Heart rate accuracy across devices →
Overnight heart rate3 studies
| 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 |
| Oura Ring Gen3 | 1.67%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| Oura Ring Gen3 | 0.97Lin's concordance correlation | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring 4 | 1.94%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| Oura Ring 4 | 0.98Lin's concordance correlation | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
3 more results in the database. Heart rate accuracy across devices →
HRV (RMSSD)5 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 9 / Ultra 2 | 28.88% (MAE 20.46 ms)Mean absolute percentage error | Polar H10 + Kubios HRV | n = 39, Serial morning measurements over 14 days, 316 readings | O'Grady et al. (2024)Independent |
| 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 |
| Oura Ring 4 | 5.96%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring 4 | 0.99Lin's concordance correlation | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| Oura Ring Gen3 | 7.15%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
5 more results in the database. HRV accuracy across devices →
Sleep stages (4-stage)7 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 8 | κ = 0.53Cohen's kappa | Polysomnography (PSG) | n = 62, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
| Apple Watch Series 8 | 50.5–86.1% (range across stages)Sensitivity | Polysomnography (PSG) | n = 35, Inpatient, 1 night | Robbins et al. (2024)Other maker funded |
| Apple Watch Series 8deep sleep duration | Deep sleep −43 minMean bias (signed) | Polysomnography (PSG) | n = 35, Inpatient, 1 night | Robbins et al. (2024)Other maker funded |
| 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 |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| 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 8 | κ = 0.3Cohen's kappa | Polysomnography (PSG) | n = 26, Two Korean sleep centres, in-lab PSG | Lee et al. (2023)Independent |
10 more results in the database. Sleep accuracy across devices →
Sleep vs wake (2-stage)8 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 8 | > 90% (all devices)Sensitivity | Polysomnography (PSG) | n = 62, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
| Apple Watch Series 8 | ≥ 95%Sensitivity | Polysomnography (PSG) | n = 35, Inpatient, 1 night | Robbins et al. (2024)Other maker funded |
| 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 |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring Gen3 | ≥ 95%Sensitivity | Polysomnography (PSG) | n = 35, Inpatient, 1 night | Robbins et al. (2024)Maker funded |
| Oura Ring Gen3 (OSSA 2.0) | 91.7–91.8%Epoch-by-epoch agreement | Polysomnography (PSG) | n = 96, Home ambulatory PSG, up to 3 nights | Svensson et al. (2024)Maker funded |
9 more results in the database. Sleep accuracy across devices →
Total sleep time4 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring | −75.5 min (older adults)Mean bias (signed) | Polysomnography (PSG) | n = 19, 1 night | Searles et al. (2026)Funding not reported |
| Oura Ring (Gen2) | −32.8 to −47.3 minMean bias (signed) | Polysomnography (PSG) | n = 53, Sleep laboratory, multiple nights, 3 sleep-opportunity conditions | Chee et al. (2021)Maker funded |
| Oura Ring | Group-level TST difference < 12 minStudy finding (no single number) | Polysomnography (PSG) | University sleep laboratory, clinical patients | Herberger et al. (2025)Independent |
| Oura Ring (Gen2) | r = 0.86Pearson correlation | Research actigraphy | n = 45, Home, 7 days | Asgari Mehrabadi et al. (2020)Independent |
Blood oxygen (SpO2)8 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 7 | 3.5% (rest)Root-mean-square error | Medical-grade pulse oximeter | n = 36, Rest, COPD outpatients | Støve et al. (2023)Funding not reported |
| 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 7 | 2.2% (RMSE 2.9%)Mean absolute error | Medical-grade pulse oximeter | n = 49, Spot readings, with and without chronic pulmonary disease | Jiang et al. (2023)Independent |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 7 | 2.9%Root-mean-square error | Medical-grade pulse oximeter | n = 49, Spot readings, with and without chronic pulmonary disease | Jiang et al. (2023)Independent |
| Apple Watch Series 8 | Met ISO RMS ≤ 4% at normoxia and SpO2 < 90%; lowest bias and RMSD of the threeStudy finding (no single number) | Medical-grade pulse oximeter | n = 18, Induced hypoxemia (FiO2 14%, 12%, 10%), ISO 80601-2-61 | Walzel et al. (2023)Independent |
4 more results in the database. SpO2 accuracy across devices →
Atrial fibrillation detection4 studies
| 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 + KardiaBand (SmartRhythm 2.0)AF episodes ≥ 1 h | 97.5% episode sensitivity (PPV 39.9%)Sensitivity | Insertable cardiac monitor | n = 24, Ambulatory, 31,348.9 h of recordings | Wasserlauf et al. (2019)Funding not reported |
| Apple Watch (irregular rhythm notification)PPG irregular pulse notification | PPV 0.84 (95% CI 0.76–0.92)Positive predictive value | ECG patch | n = 419297, Siteless pragmatic study; ECG patch after notification | Perez et al. (2019)Maker funded |
More results (1)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Kardia Band on Apple Watch (single-lead ECG)automated ECG read; 57 of 169 recordings non-interpretable | Sens 93% / spec 84% (interpretable recordings)Sensitivity | 12-lead ECG | n = 100, Before and after cardioversion | Bumgarner et al. (2018)Funding not reported |
VO2max estimate3 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 10 | 13.2% (MAE 6.79 mL/kg/min)Mean absolute percentage error | Indirect calorimetry | n = 40, Maximal treadmill test (modified Åstrand) | Lambe et al. (2026)Independent |
| Apple Watch | 13.31% (MAE 6.92 mL/kg/min)Mean absolute percentage error | Indirect calorimetry | n = 30, Maximal treadmill test (modified Åstrand) | Lambe et al. (2025)Independent |
| Apple Watch Series 7 | 15.79% (ICC 0.47)Mean absolute percentage error | Indirect calorimetry | n = 19, Graded cycle ergometer test | Caserman et al. (2024)Independent |
Energy expenditure (calories)8 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 9 | Inconsistent across all groupsStudy finding (no single number) | Indirect calorimetry | n = 30, 10-min treadmill | Chase et al. (2024)Independent |
| Apple Watch Series 4 | 13.5%–27.1% (range by intensity)Coefficient of variation | Indirect calorimetry | n = 25, Sitting, walking, running, sprints | Düking et al. (2020)Independent |
| 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 8physical activity energy expenditure, 10 min | +21.6 kcalMean bias (signed) | Indirect calorimetry | n = 52, 10-min recumbent cycling intervals | Kostrna et al. (2026)Independent |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Apple Watch Series 6walking | 19.8% walk / 24.4% runMean absolute percentage error | Indirect calorimetry | n = 20, Outdoor 2-km walk (6 km/ | Le et al. (2022)Independent |
| Apple Watch | Lowest EE error of 7 devices, but no device below 20%Study finding (no single number) | Indirect calorimetry | n = 60, Sitting, walking, running, cycling | Shcherbina et al. (2017)Independent |
2 more results in the database. Calories accuracy across devices →
Verdict
For sleep tracking Oura did better on staging in the one head-to-head study and lasts days rather than hours; for cardiac features and daytime use Apple Watch adds ECG and closer heart-rate agreement. Many people wear both.
Frequently asked questions
Is Oura Ring HRV more accurate than Apple Watch?
Not clearly. In Miller et al. (2022), overnight HRV ICC vs ECG was 0.67 for Apple Watch S6 and 0.63 for Oura Gen 2, with absolute biases of 22.5 and 18.9 ms.
Can Apple Watch match Oura Ring for sleep tracking?
In Miller et al. (2022), Oura Gen 2 matched polysomnography sleep stages in 61% of epochs (κ 0.43) versus 53% (κ 0.20) for Apple Watch S6; for sleep vs wake they were 89% and 88%. In Lee et al. (2023), four-stage kappa was 0.35 for Oura Gen3 and 0.30 for Apple Watch Series 8.
Should I wear both Apple Watch and Oura Ring?
They do different jobs: Oura's multi-day battery suits sleep tracking, while Apple Watch adds ECG, notifications and closer daytime heart-rate agreement.
Device research records
Datasets, papers and validation results for the models named on this page.