Apple Watch vs Garmin Accuracy: Who Wins on Each of 11 Metrics
Last Updated: November 9, 2026
Apple Watch is more accurate than Garmin on most metrics, but not on all of them. Across the peer-reviewed studies that tested both brands, Apple came out ahead on 5 of 11 measures and Garmin on 1. Resting heart rate leans Apple in a test that was not like for like, steps were a tie, HRV has no fair comparison yet, and two metrics have no data for either brand. In the one lab sleep study that put both on the same people, Apple Watch scored 0.53 on sleep-stage agreement and Garmin 0.21. Garmin led on VO2 max, with a 6.7% error in trained runners wearing a chest strap against Apple Watch's 13.2%. The gaps on heart rate during exercise are small. The gaps on sleep and blood oxygen are not. For the wider picture across seven brands, see are fitness trackers accurate.
Want to compare every brand by metric yourself? Open the wearable accuracy hub, then come back for the Apple vs Garmin detail.
I started this expecting a split decision, because Garmin owns the running crowd and Apple owns everyone else. Then I went through the studies that strapped both watches onto the same people at the same time, and the pattern was hard to miss. Apple was closer more often, and the biggest gaps were at night, not on the run. Every deciding figure below comes from the paper's own results tables, and no study here was paid for by Apple or Garmin.
The scorecard
One verdict per metric, grouped by result. The figures and studies behind each verdict are in the sections below.
Metric | Winner | In plain terms |
Sleep stages | 🍎 Apple Watch | Matched the lab on sleep stages more than twice as well |
Sleep timing | 🍎 Apple Watch | Garmin added about 40 extra minutes of sleep a night, Apple about 20 |
Exercise heart rate | 🍎 Apple Watch (narrowly) | Closer in 4 of 6 tests, gaps mostly under 1 bpm |
Blood oxygen | 🍎 Apple Watch | Garmin barely changed when oxygen levels dropped |
Calories | 🍎 Apple Watch | Both are off, Garmin about twice as far during cycling |
VO2 max | ⌚ Garmin | Closer for fit runners wearing a chest strap |
Resting heart rate | Leans Apple | Only one test, and the two watches were not measured the same way |
Steps | Tie | Both count a few percent extra |
HRV | Too early to tell | Apple changed how it measures HRV in 2026 |
Breathing rate | No data | Not tested in healthy adults |
Skin temperature | No data | Never independently tested |
Models tested: sleep is Apple Watch Series 8 vs Garmin Vivosmart 4; resting heart rate is Series 6 vs Forerunner 245; cycling heart rate and calories are Series 8 vs Forerunner 955; VO2 max is Series 10 vs Forerunner 245 with a Polar H10 strap.
How to read these numbers
Three terms do most of the work in this post, so here they are in plain English.
Kappa scores how often a watch agrees with a lab sleep test on which stage you are in, after removing lucky guesses. Zero is chance, 1 is perfect.
MAPE (mean absolute percentage error) is how far off a reading is on average, as a percent. Lower is better.
Bias is whether a watch reads high or low on average. A watch can have a small bias and still be far off on single readings.
Sleep stages: Apple's clearest win
Brand | Figure | Model tested | Study | n |
Apple Watch | Kappa 0.53 | Series 8 | Schyvens 2025 | 20 |
Garmin | Kappa 0.21 | Vivosmart 4 | Schyvens 2025 | 25 |
Apple Watch | Kappa 0.60 | Series 8 | Robbins 2024, healthy | 29 |
Garmin | Kappa 0.25 | Forerunner 245 Music | Miller 2022, healthy | 53 |
The only lab study that tested both brands' own sleep staging on the same people is Schyvens 2025. Against a full lab sleep test, Apple Watch Series 8 scored a four-stage kappa of 0.53 and Garmin Vivosmart 4 scored 0.21. Apple Watch caught 68.6% of REM sleep and Garmin 33.1%. On deep sleep the two were close, 50.7% for Apple and 47.5% for Garmin.
About half of the Schyvens 2025 group had suspected sleep apnea, so the cross-check uses healthy adults only. In Robbins 2024, Apple Watch Series 8 scored a kappa of 0.60. In Miller 2022, Garmin Forerunner 245 Music scored 0.25. Those are two different studies, but they point the same way, and the gap is about as wide.
The Garmin model matters here. Schyvens 2025 tested a Vivosmart 4 fitness band, and no lab sleep study has tested a Fenix 6 or later, a Forerunner 255 or later, or any Venu from the Venu 2 on. For how Apple stacks up against rings and other watches, see our most accurate sleep tracker comparison.
Sleep timing: Garmin adds about 40 minutes
Brand | Extra sleep counted | Awake time caught | Model tested | Study | n |
Apple Watch | +19.6 min | 52.2% | Series 8 | Schyvens 2025 | 20 |
Garmin | +38.4 min | 29.4% | Vivosmart 4 | Schyvens 2025 | 25 |
Most watches count some awake time as sleep, so the useful test is how much lying awake they catch. In Schyvens 2025, Apple Watch Series 8 caught 52.2% of awake time and Garmin Vivosmart 4 caught 29.4%. Apple Watch added 19.6 minutes of sleep a night and Garmin added 38.4 minutes.
The Garmin pattern holds across models and studies. Garmin Forerunner 245 Music added 43.8 minutes in Miller 2022, and in Chinoy 2021 the Fenix 5S added 43.7 minutes and the Vivosmart 3 added 46.8. Garmin caught only 18% to 30% of awake time across these three studies.
Using both watches
Plenty of people own both, or switch between them. Kygo connects Apple Health and Garmin at the same time, so you can take sleep from the device that scored better on sleep and VO2 max from the one that scored better there. It also shows how what you eat moves those numbers, night by night.
HRV: no winner yet, and here is why
Brand | Figure | What was measured | Model tested | Study | n |
Apple Watch | 28.9% off | SDNN, 5-min morning reading | Series 9, Ultra 2 | O'Grady 2024 | 39 |
Garmin | 10.5% off | RMSSD, overnight | Fenix 6 | Dial 2025 | 13 |
Apple Watch | ICC 0.67 | RMSSD, overnight, third-party app | Series 6 | Miller 2022 | 53 |
Garmin | ICC 0.24 | RMSSD, 3-min reading before bed | Forerunner 245 | Miller 2022 | 53 |
Garmin Fenix 6 was 10.5% off a chest-strap ECG on overnight HRV in Dial 2025. Apple Watch Series 9 and Ultra 2 were 28.9% off in O'Grady 2024. Those two numbers look like a Garmin win, but they measure different things. Garmin reports RMSSD from the whole night, while every study of Apple's own HRV reading so far tested its older SDNN method, taken in short readings.
The one study of both on the same people, Miller 2022, points the other way. Apple Watch Series 6 scored an agreement of 0.67 and Garmin Forerunner 245 scored 0.24, on a scale where 1 is perfect. But Apple's reading came from a third-party app overnight, and Garmin's from a 3-minute reading taken awake before bed.
Apple also changed how it measures HRV in September 2026. Series 12 and Ultra 4 now give two readings, Recovery HRV and Overall HRV, measured as often as every five minutes (Apple Newsroom, Apple Support). iOS 27 added an RMSSD type to Apple Health next to SDNN, according to developer reporting, so at least one new reading likely uses RMSSD. Apple has not said which reading uses which. No independent study has tested either one yet, so a fair Apple vs Garmin HRV test does not exist. Our guide to how accurate your heart rate monitor is covers HRV across all brands.
Resting heart rate: leans Apple, with a catch
Brand | Bias | Agreement (ICC) | Model tested | Study | n |
Apple Watch | +0.5 bpm | 0.96 | Series 6 | Miller 2022 | 53 |
Garmin | +5.0 bpm | 0.41 | Forerunner 245 | Miller 2022 | 53 |
In Miller 2022, Apple Watch Series 6 read resting heart rate 0.5 bpm high on average, and Garmin Forerunner 245 read 5.0 bpm high. That is the only test of both brands on the same people. It is not like for like: Garmin's reading came from a 3-minute check taken awake before bed, while Apple's came from the sleep period, and the authors say awake sampling may explain Garmin's lower agreement.
There is no newer tie-breaker. Apple Watch Series 9 and Ultra 2 were 5.9% off on morning resting heart rate in O'Grady 2024, with no matching Garmin test. Dial 2025 tried to test Garmin Fenix 6 overnight resting heart rate but had to drop it because Garmin's timestamps could not be lined up with the chest strap.
Exercise heart rate: close, with Apple slightly ahead
Activity | Apple Watch (model) | Garmin (model) | Study | n |
Cycling, avg error | 2.51 bpm (Series 8) | 2.93 bpm (Forerunner 955) | Kostrna 2026 | 58 |
Weight training, MAPE | 3.79% (Series 8) | 5.17% (Vivosmart 5) | Yun 2026 | 70 |
Rest, stress, walking, MAPE | 7.3% (SE) | 6.3% (Vivoactive 5) | Gielen 2026 | 45 |
Graded cycling, missing data | 7% (Series 8) | 20% (Vivosmart 5) | Mulholland 2025 | 28 |
Max cycle test, MAPE | 0.91% to 1.74% (Series 6) | 1.16% to 2.15% (Forerunner 945) | Ho 2022 | 30 |
Treadmill / weights, bias | -0.97 / -0.53 bpm (Series 7) | +0.35 / +2.56 bpm (Vivosmart 5) | Lee 2026 | 62 |
Six studies tested exercise heart rate on Apple Watch and Garmin on the same people. Apple Watch was closer in four (Kostrna 2026, Yun 2026, Mulholland 2025, Ho 2022), Garmin was closer in one (Gielen 2026), and Lee 2026 split: Garmin had the smaller bias on the treadmill, Apple on weights. Most gaps were under 1 bpm or about 1 percentage point.
The bigger practical gap is missing data. In Mulholland 2025, Garmin Vivosmart 5 dropped 20% of readings during cycling and Apple Watch Series 8 dropped 7%. A 2026 meta-analysis of 39 studies (Sicbaldi 2026) found pooled biases of -0.62 bpm for Apple and -0.91 bpm for Garmin, which is effectively a tie on average.
Model matters on both sides. Garmin's weaker results mostly come from its Vivosmart bands, while the Forerunner 955 and Vivoactive 5 ran close to Apple. Garmin's one win came against an Apple Watch SE, which uses an older sensor than the flagship Series. For results by sport, see heart rate accuracy by activity type.
Blood oxygen: Apple ahead
Brand | Figure | Model tested | Study | n |
Apple Watch | 2.2 Arms, bias -0.1 | Series 8 | Walzel 2023 | 18 healthy adults |
Garmin | CCC 0.10, read 95.4% vs 92.1% | Fenix 6 | Carrier 2025 | 22 healthy adults |
In healthy adults breathing low-oxygen air, Apple Watch Series 8 had an average error of 2.2 percentage points (Walzel 2023), inside the usual pass mark of 4 or less. In a separate altitude study, Garmin Fenix 6 scored a concordance of 0.10, where 1 is perfect, and barely moved when oxygen fell (Carrier 2025). Garmin Fenix 6 also gave a reading only 59% of the time.
These are two different studies and two different statistics, so the comparison is a direction, not a precise gap. Tests in hospital patients that wore both brands point the same way: Apple Watch Series 7 was 2.44% off arterial blood and Garmin Fenix 6 Pro 3.50% (Helmer 2023).
Steps: a tie
Brand | Read vs hip sensor | Ratio range (95% CI) | Model tested | Study | n |
Apple Watch | +7% (+483/day) | 0.90 to 1.26 | Mixed | Paluch 2026 | 59 studies |
Garmin | +3% (+374/day) | 0.90 to 1.19 | Mixed | Paluch 2026 | 59 studies |
A 2026 analysis of 59 free-living studies found Apple Watch counted 7% more steps than a hip sensor and Garmin 3% more (Paluch 2026). The two ranges almost fully overlap, and the hip sensor is itself an estimate, so the authors frame it as a difference between devices rather than true accuracy. Call it a tie.
Older lab tests agree it is close. At normal walking speeds, Garmin Vivoactive 3 and Vivofit 3 were 1% to 2% off and Apple Watch Series 1 4% off (Mora-Gonzalez 2022), but across the full speed range including slow walking, Apple matched or beat Garmin. Our step count accuracy post has every model.
Calories: Apple ahead, but both are rough
Activity | Apple Watch (model) | Garmin (model) | Study | n |
10-min cycling, error | 35.7% (Series 8) | 77.6% (Forerunner 955) | Kostrna 2026 | 51 to 52 |
Weight training, MAPE | 112.2% (Series 8) | 114.9% (Vivosmart 5) | Yun 2026 | 70 |
Endurance treadmill, gap | 14.3% (Series 7) | 30.5% (Vivosmart 5) | Lee 2026 | 62 |
Outdoor walk / run, MAPE | 19.8% / 24.4% (Series 6) | 32.0% / 21.8% (Fenix 6) | Le 2022 | 20 |
Apple Watch was closer on calories in most same-people tests. In 10 minutes of cycling, Apple Watch Series 8 was 35.7% off and Garmin Forerunner 955 77.6% (Kostrna 2026). In weight training both brands were more than 100% off, Apple Watch at 112.2% and Garmin at 114.9% (Yun 2026). For weight loss, where these errors matter most, see the best fitness tracker for weight loss.
Lee 2026 found Apple Watch Series 7 14.3% from a gas analyzer on a treadmill and Garmin Vivosmart 5 30.5%. The paper's tables show both reading high, while its text says both read low, so the direction is not settled. Apple is closer either way.
Garmin's one calorie win comes from Perez 2025, a conference abstract with no full paper: Garmin Forerunner 265S was 14.65% off on a max treadmill test and Apple Watch Ultra 2 25.95%. An abstract does not show its methods in full, so it does not decide this metric. Brand detail is in how accurate is Apple Watch calorie burn.
VO2 max: Garmin ahead, for fit runners
Brand | Figure | Model tested | Study | n |
Garmin | 6.7% off | Forerunner 245 + Polar H10 strap | Engel 2026 | 35 trained runners |
Garmin | 7.05% off | Fenix 6 + HRM-Run strap | Carrier 2025 | 19 |
Apple Watch | 13.2% off, reads low | Series 10 | Lambe 2026 | 35, mostly very fit |
Garmin | 56% median error, wrist only | Vivoactive 4S | Jamieson 2024 | 207 |
Garmin estimated VO2 max within 6.7% of a lab test in trained runners and triathletes using a chest strap (Engel 2026), and within 7.05% in Carrier 2025, also with a strap. Apple Watch Series 10, wrist only, was 13.2% off and read low in Lambe 2026. No study has tested both on the same people.
The Garmin edge comes with conditions. Both strong Garmin results used a chest strap and fit runners. In a general group of 207 adults (79% women, median age 56), the wrist-only Garmin Vivoactive 4S had a median error of 56% on a cycle test (Jamieson 2024). For more, see the most accurate VO2 max wearable ranking.
Breathing rate and skin temperature: no data
Neither brand has a usable breathing rate test in healthy adults. In the one study of both, run on hospital ward patients, Apple Watch Series 7 produced no breathing rate readings and Garmin Fenix 6 Pro had a correlation of 0.28 with the reference (Helmer 2024). Neither Apple nor Garmin has an independent test of its skin temperature sensor against a thermometer.
Which one should you trust for what
If sleep, blood oxygen or everyday heart rate is the number you check most, the studies favor Apple Watch. If VO2 max for running is your main number and you train with a chest strap, the studies favor Garmin. For steps, either is fine.
Whichever you wear, compare it with itself. A watch that is 10% off tends to be off in the same way night after night, so your own trend is more useful than any single reading.
Common questions
Is Apple Watch or Garmin more accurate?
Apple Watch is more accurate on most metrics. In peer-reviewed tests it led on 5 of 11 measures, including sleep stages and blood oxygen, while Garmin led on VO2 max, steps were a tie and HRV has no fair comparison yet.
What does the research say about Apple Watch vs Garmin accuracy for sleep?
Apple Watch is clearly ahead on sleep. In the one lab study of both on the same people, Apple Watch Series 8 scored a sleep-stage kappa of 0.53 and Garmin Vivosmart 4 scored 0.21, and Garmin added about 38 minutes of sleep a night against Apple's 20.
Which is more accurate for heart rate during exercise?
Apple Watch, but only narrowly. It was closer in four of six same-people studies, and most gaps were under 1 bpm, so either watch is fine for training zones.
Is Garmin or Apple Watch better for HRV?
There is no fair answer yet. Garmin reports overnight RMSSD, every study of Apple's own HRV reading tested its older SDNN method, and no independent study has tested the new HRV readings Apple added to Series 12 and Ultra 4 in September 2026.
Which is more accurate for VO2 max?
Garmin, for fit runners using a chest strap: 6.7% off a lab test, against 13.2% for Apple Watch Series 10. A wrist-only Garmin was much further off in a general group of adults.
Is Apple Watch vs Garmin accuracy different for calories?
Yes, but both are rough. Apple Watch was closer in most same-people tests, for example 35.7% off during cycling against 77.6% for Garmin, and both were more than 100% off during weight training.
Are Apple Watch and Garmin step counts accurate?
Close enough for everyday use, and tied with each other. Across 59 studies, Apple Watch counted 7% more steps than a hip sensor and Garmin 3% more, with overlapping ranges.
Did Apple or Garmin pay for these studies?
No. None of the studies in this post was funded by Apple or Garmin. A few had other industry links, which are flagged in the sources below.
The bottom line
Is Apple Watch or Garmin more accurate? On most metrics, Apple Watch. It led on 5 of 11 in peer-reviewed tests, with the clearest gaps on sleep (kappa 0.53 vs 0.21) and blood oxygen. Garmin led on VO2 max for fit runners with a chest strap, steps were a tie, and HRV has no fair test yet after Apple's 2026 change.
Wear both, or switching between them? Kygo pulls Apple Health and Garmin into one place and uses the stronger device for each metric. Get it on iOS or Android.
Key sources: Schyvens 2025 (Sleep Advances, 62 adults, Flemish government funded); Robbins 2024 (Sensors, Oura-funded, lead author on Oura's advisory board); Miller 2022 (Sensors, 53 adults, lab receives WHOOP support); Chinoy 2021 (Sleep, US Navy funded); Dial 2025 (Physiological Reports, Air Force Research Laboratory funded); O'Grady 2024 (Sensors, 39 adults); Kostrna 2026, heart rate (Sensors, 58 adults); Kostrna 2026, calories (PLOS ONE); Yun 2026 (Bioengineering, 70 men); Gielen 2026 (JMIR Formative Research); Mulholland 2025 (European Journal of Applied Physiology, devices supplied by SlateSafety); Lee 2026 (Sensors, SOLUM Health Care grant, one author employed by SOLUM); Ho 2022 (Digital Health); Sicbaldi 2026 (Forensic Science International, 39-study meta-analysis, two authors co-founded mHealth Technologies); Walzel 2023 (Sensors, induced hypoxia); Carrier 2025 (Sensors); Helmer 2023 (iScience); Helmer 2024 (Digital Health); Paluch 2026 (Journal of Sport and Health Science, 59 studies); Mora-Gonzalez 2022 (IJBNPA, NIH funded); Le 2022 (Frontiers in Physiology, Huawei funded); Engel 2026 (European Journal of Applied Physiology); Lambe 2026 (Mayo Clinic Proceedings: Digital Health); Jamieson 2024 (Computing in Cardiology); Perez 2025 (conference abstract only).
A note on sources: Perez 2025 exists only as a conference abstract, so it is reported but does not decide the calorie verdict, and the abstract lists two Apple results without saying which is which. The HRV, blood oxygen and VO2 max comparisons draw Apple and Garmin from different studies, so treat those gaps as direction rather than exact size. Patient studies are used only to confirm direction, never as the deciding figure.
Disclaimer: Kygo is a personal data aggregation and insights platform designed for informational purposes only. The information provided by Kygo, including correlations, patterns, and trends identified in your data, does not constitute medical advice, diagnosis, or treatment. Always consult a licensed healthcare provider with any questions regarding medical conditions.
Which one is on your wrist, and is there a number on it you have stopped trusting? Tell me at Ryan@kygo.app, I read every reply.