Device comparisons
Whoop vs Oura Ring: Which Tracks Sleep and HRV Better?
WHOOP is a screenless band worn on the wrist or body; Oura is a ring worn on the finger. Two peer-reviewed studies tested both on the same people. Miller et al. (2022; 53 adults, one night with polysomnography and ECG) found WHOOP 3.0 and Oura Gen 2 close for sleep staging (60% vs 61% epoch agreement) and WHOOP closer for overnight HRV (ICC 0.99 vs 0.63); WHOOP supplied its raw data and funds the lab's research. Dial et al. (2025; 13 adults, 536 nights at home against ECG, no competing interests) tested the newer hardware and found the opposite for HRV: overnight RMSSD error was 5.96% for Oura Ring 4 and 7.15% for Oura Gen3 versus 8.17% for WHOOP 4.0. Resting heart rate error was 1.94%, 1.67% and 3.00%.
Published study results
| Metric | WHOOP 4.0 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Sleep stagesEpoch agreement vs PSGMiller et al. 2022, Sensors | 60%κ 0.44 · WHOOP 3.0 | 61%κ 0.43 · Oura Gen 2 |
| Sleep vs wakeEpoch agreement vs PSGMiller et al. 2022, Sensors | 86%κ 0.44 · WHOOP 3.0 | 89%κ 0.51 · Oura Gen 2 |
| Overnight HRVICC vs ECGMiller et al. 2022, Sensors | 0.99WHOOP 3.0Closer in this study | 0.63Oura Gen 2 |
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
WHOOP 4.0 Onyx SuperKnit band: product photograph from WHOOP’s listing. Oura Ring 4 in silver: product photograph from Oura.
Quick answer
Neither is clearly more accurate. In a WHOOP-supported sleep-lab study, WHOOP 3.0 tracked overnight HRV more closely than Oura Gen 2 (ICC 0.99 vs 0.63) and sleep staging was a tie (60% vs 61%). In a later independent study, Oura Ring 4 and Gen3 were closer to ECG for overnight HRV than WHOOP 4.0 (error 5.96% and 7.15% vs 8.17%).
Sources: Miller et al. 2022, Sensors; Dial et al. 2025, Physiological Reports
At a glance
Each row is one statistic from one study already cited on this page. Different statistics are not ranked against each other. Miller et al. 2022: WHOOP supplied raw data and the lab receives WHOOP research support. Dial et al. 2025 reported no competing interests. Figures apply to the named models, not every WHOOP or Oura product.
| Specification | WHOOP 4.0 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Sleep stagesEpoch agreement vs PSGNear tie | 60%κ 0.44 · WHOOP 3.0 | 61%κ 0.43 · Oura Gen 2 |
| Sleep vs wakeEpoch agreement vs PSGNear tie | 86%κ 0.44 · WHOOP 3.0 | 89%κ 0.51 · Oura Gen 2 |
| Overnight HRVICC vs ECG | 0.99WHOOP 3.0Closer in this study | 0.63Oura Gen 2 |
| Overnight HRVMAPE vs ECG | 8.17%WHOOP 4.0 | 5.96% / 7.15%Ring 4 / Gen3Closer in this study |
| Resting heart rateMAPE vs ECGNear tie | 3.00%WHOOP 4.0 | 1.94% / 1.67%Ring 4 / Gen3 |
Primary rows only. The study tables further down list more results from the accuracy database.
Miller et al. 2022, Sensors; Dial et al. 2025, Physiological Reports
Hardware specs
| Specification | WHOOP 4.0 | Oura Ring (Gen3 / Ring 4) |
|---|---|---|
| Form factorDiffers | Screenless band (wrist or WHOOP Body garments) | Finger ring |
| Optical sensorDiffers | 5 LEDs (3 green, 1 red, 1 infrared), 4 photodiodes | Ring 4: 18-path PPG (green/IR for HR, red/IR for SpO2) |
| Battery LifeDiffers | Five days (WHOOP) | Up to 7 days (Gen3); typically 5–8 days (Ring 4) |
| Water ResistanceDiffers | — | 100 m |
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), Dial et al. 2025, Physiological Reports (Oura Gen3, Ring 4, WHOOP 4.0 nocturnal HR and HRV vs ECG, n=13), Bellenger et al. 2021, Sensors (WHOOP HR and HRV vs ECG), Stone et al. 2021, Front Sports Act Living (resting HRV), Gillinov et al. 2017, Med Sci Sports Exerc (exercise HR vs ECG, n=50), WHOOP: Introducing WHOOP 4.0, 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
WHOOP 4.0
Pros
- Overnight HRV ICC 0.99 vs ECG for WHOOP 3.0 in Miller 2022 (Oura Gen 2: 0.63)
- Heart-rate bias ≤0.39% vs ECG in Bellenger 2021
- Can be worn on the wrist or in WHOOP Body garments
Cons
- Overnight HRV error 8.17% vs ECG for WHOOP 4.0 in Dial 2025 (Oura Ring 4: 5.96%)
- Five-day battery, shorter than Oura Gen3's up to 7 days
- Requires a WHOOP membership
- No screen
Oura Ring (Gen3 / Ring 4)
Pros
- Ring form factor; Gen3 battery up to 7 days, Ring 4 typically 5–8 days
- Water resistant to 100 m
- Sleep-stage agreement 61% (κ 0.43) for Oura Gen 2 in Miller 2022
- Overnight HRV error 5.96% (Ring 4) and 7.15% (Gen3) vs ECG in Dial 2025, below WHOOP 4.0's 8.17%
Cons
- Overnight HRV ICC 0.63 vs ECG for Oura Gen 2 in Miller 2022
- Detailed sleep, 24/7 heart rate and SpO2 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 rest2 studies
Only maker-funded evidence for WHOOP on this metric.
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP | ≤ 0.39 ± 0.38%Mean bias (signed) | ECG | Rest, 15 opportunities | Bellenger et al. (2021)Maker funded |
| 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 exercise3 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 3.0 | High agreement only in squats; low in rows and burpeesStudy finding (no single number) | ECG chest strap (Polar H7/ | n = 29, Resistance exercise (5 exercises) | Støve et al. (2022)Funding not reported |
| WHOOP 4.0 (upper arm) | Strongest agreement (with Verity Sense) in graded treadmillStudy finding (no single number) | ECG chest strap (Polar H7/ | n = 28, Rest, warm-up, burpees, Bruce treadmill | Moghaddam et al. (2025)Funding not reported |
| Oura Ring Gen3mixed rest/stress/walking | 9–14 bpm (group range)Mean absolute error | ECG chest strap (Zephyr BioHarness / | n = 45, Rest, cognitive stress, steady and intermittent walking in neutral/ | Gielen et al. (2026)Funding not reported |
Overnight heart rate3 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 4.0 | 3.00%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| WHOOP 4.0 | 0.91Lin's concordance correlation | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| WHOOP 3.0 | ICC 0.99Intraclass correlation | ECG | n = 53, Overnight, sleep laboratory | Miller et al. (2022)Maker funded |
| WHOOP 3.0 | 0.7 bpm (absolute bias)Mean absolute error | ECG | n = 53, Overnight, sleep laboratory | Miller et al. (2022)Maker funded |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| 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 |
5 more results in the database. Heart rate accuracy across devices →
HRV (RMSSD)5 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 4.0 | 8.17%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| WHOOP 4.0 | 0.94Lin's concordance correlation | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
| WHOOP | Ln RMSSD 1.66 ± 1.80% (LoA ±5.93%)Mean bias (signed) | ECG | Rest, 15 opportunities | Bellenger et al. (2021)Maker funded |
| WHOOP 3.0 | ICC 0.99Intraclass correlation | ECG | n = 53, Overnight, sleep laboratory | Miller et al. (2022)Maker funded |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 3.0 | 4.7 ms (absolute bias)Mean absolute error (absolute bias) | ECG | n = 53, Overnight, sleep laboratory | Miller et al. (2022)Maker funded |
| Oura Ring 4 | 5.96%Mean absolute percentage error | ECG | n = 13, Home, during sleep, 536 nights | Dial et al. (2025)Independent |
7 more results in the database. HRV accuracy across devices →
Sleep stages (4-stage)9 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP (strap, 2.0 era) | 64% (κ 0.47)Epoch-by-epoch agreement | Polysomnography (PSG) | n = 12, Sleep laboratory, 10-day protocol, 86 sleeps | Miller et al. (2020)Funding not reported |
| WHOOP (strap, 2.0 era) | κ = 0.47Cohen's kappa | Polysomnography (PSG) | n = 12, Sleep laboratory, 10-day protocol, 86 sleeps | Miller et al. (2020)Funding not reported |
| WHOOP (auto-detect) | 63%Epoch-by-epoch agreement | Polysomnography (PSG) | n = 6, Sleep laboratory, 9 nights, 54 sleeps | Miller et al. (2021)Maker funded |
| WHOOP 3.0 | 60%Epoch-by-epoch agreement | Polysomnography (PSG) | n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together | Miller et al. (2022)Maker funded |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 3.0 | κ = 0.44Cohen's kappa | Polysomnography (PSG) | n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together | Miller et al. (2022)Maker funded |
| WHOOP 4.0 | κ = 0.37Cohen's kappa | Polysomnography (PSG) | n = 40, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
9 more results in the database. Sleep accuracy across devices →
Sleep vs wake (2-stage)10 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 4.0 | > 90% (all devices)Sensitivity | Polysomnography (PSG) | n = 62, Sleep laboratory, 1 night | Schyvens et al. (2025)Funding not reported |
| WHOOP (strap, 2.0 era) | 89% (κ 0.49)Epoch-by-epoch agreement | Polysomnography (PSG) | n = 12, Sleep laboratory, 10-day protocol, 86 sleeps | Miller et al. (2020)Funding not reported |
| WHOOP (strap, 2.0 era) | κ = 0.49Cohen's kappa | Polysomnography (PSG) | n = 12, Sleep laboratory, 10-day protocol, 86 sleeps | Miller et al. (2020)Funding not reported |
| WHOOP (auto-detect) | 86%Epoch-by-epoch agreement | Polysomnography (PSG) | n = 6, Sleep laboratory, 9 nights, 54 sleeps | Miller et al. (2021)Maker funded |
More results (2)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP 3.0 | 86%Epoch-by-epoch agreement | Polysomnography (PSG) | n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together | Miller et al. (2022)Maker funded |
| WHOOP 3.0 | κ = 0.44Cohen's kappa | Polysomnography (PSG) | n = 53, Sleep laboratory, 1 night, 9 h in bed, all devices worn together | Miller et al. (2022)Maker funded |
11 more results in the database. Sleep accuracy across devices →
Total sleep time5 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| WHOOP (strap, 2.0 era) | +8.2 ± 32.9 min (n.s.)Mean bias (signed) | Polysomnography (PSG) | n = 12, Sleep laboratory, 10-day protocol, 86 sleeps | Miller et al. (2020)Funding not reported |
| 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 |
More results (1)
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring (Gen2) | r = 0.86Pearson correlation | Research actigraphy | n = 45, Home, 7 days | Asgari Mehrabadi et al. (2020)Independent |
Energy expenditure (calories)2 studies
| Device tested | Result | Reference | Sample | Study |
|---|---|---|---|---|
| Oura Ring (Gen2)total energy expenditure | r = 0.70Pearson correlation | Actiheart / | n = 21, Free-living, up to 7 days | Henriksen et al. (2022)Independent |
| Oura Ring (Gen2) | r = 0.93 (lab)Pearson correlation | Indirect calorimetry | Laboratory activities | Kristiansson et al. (2023)Independent |
Verdict
The two head-to-head studies disagree on HRV: WHOOP 3.0 beat Oura Gen 2 in a WHOOP-supported sleep-lab study, while Oura Gen3 and Ring 4 were closer to ECG than WHOOP 4.0 in a smaller independent study at home. Overnight heart rate was close to ECG for all of them, and sleep staging was a near tie in the one study that measured it. Both are small studies of healthy adults. Oura offers a ring and slightly longer battery; WHOOP offers body placement options. Both need a membership for full features.
Frequently asked questions
Which is more accurate for HRV: WHOOP or Oura Ring?
It depends on the generation. In Miller et al. (2022), overnight RMSSD from WHOOP 3.0 agreed with ECG at ICC 0.99 (absolute bias 4.7 ms) versus 0.63 (18.9 ms) for Oura Gen 2; WHOOP supplied raw data and the lab receives WHOOP research support. In the independent Dial et al. (2025) study of 13 adults over 536 nights, overnight RMSSD error against ECG was 5.96% for Oura Ring 4, 7.15% for Oura Gen3 and 8.17% for WHOOP 4.0.
Which tracks sleep stages better: WHOOP or Oura?
Close to a tie. Against polysomnography, Oura Gen 2 had 61% epoch agreement (κ 0.43) and WHOOP 3.0 60% (κ 0.44) in Miller et al. (2022). For sleep vs wake both were 86–89%.
Can WHOOP or Oura Ring replace a medical heart rate monitor?
No. Both are consumer wellness devices. For clinical rhythm assessment use an ECG; for exercise heart rate a chest strap such as the Polar H7 reached 0.996 concordance with ECG in Gillinov et al. (2017).
Do WHOOP and Oura need a subscription?
WHOOP is sold as a membership. Oura Ring works without a membership but then shows only Readiness, Sleep and Activity scores; detailed sleep, 24/7 heart rate and SpO2 need a membership (Oura).
Device research records
Datasets, papers and validation results for the models named on this page.