⌚ How Accurate Are Fitness Trackers? Fitbit, Garmin, Apple, Oura, and Withings Compared

These days, tracking your health is more accessible than ever thanks to the widespread distribution and use of wearable fitness trackers. But how accurate is your health tracker? Are you really taking those 10,000 steps a day, or did you burn that many calories on your morning 5K run? Guava Health examines the accuracy of activity trackers from five leading fitness tracker companies—Fitbit, Garmin, Apple, Oura, and Withings—to understand how reliable data from wearable devices is and how effectively they can be used to monitor health behaviors.

It is important to note that the data compilation will be based on information published in peer-reviewed journals. This is because manufacturers are not legally required to disclose accuracy testing unless their products are classified as medical devices.

If you’re still having trouble making a decision when choosing a device, check out this article to help you narrow down your choices.

How accurate is Fitbit?

While step counting is Fitbit’s specialty, a review of 67 studies found some variation in accuracy. On treadmills, Fitbits tended to underestimate steps, while in real-world situations, they often overestimated them. Overall, however, these discrepancies were generally considered acceptable. Despite their success in counting steps, Fitbit’s energy expenditure measurements were less accurate, especially during higher-intensity activities, and they often underestimated distance during faster walking. Additionally, while Fitbit’s sleep tracking closely matches some research-grade tools, a more recent 2023 study found that the Fitbit Inspire 2 overestimated key sleep metrics compared to the gold standard. When compared to polysomnography (PSG) tests, researchers observed these overestimations for total sleep time, deep sleep, and REM sleep. When it comes to cardiovascular health, the Fitbit Charge does quite well. It only slightly overestimates VO2 max and slightly underestimates heart rate (HR), but becomes more accurate with increased activity. VO2 max is an important indicator of cardiovascular fitness. It measures how much oxygen your body can take in during exercise, so it tends to be higher in people who do a lot of aerobic activity, such as running or swimming.

Follows closely:Steps, VO max and sleep (sort of)

Doesn’t track accurately:Distance and energy expenditure

How accurate is a Garmin watch?

In a comprehensive 2020 review of 32 studies, Garmin activity trackers showed high step tracking accuracy, but there was limited research available on assessing speed, altitude, and sleep tracking. When it comes to distance accuracy, Garmin watches seem to overestimate distance at low treadmill speeds and underestimate at high speeds. Additionally, the accuracy of energy expenditure and heart rate tracking was found to be relatively lower than other health trackers. A 2021 study found that the Garmin Forerunner accurately predicted VO2 max, although there was significant variation across a group of 44 people.

Follows closely: Steps and VO2 max

Doesn’t track accurately:Energy Expenditure, Distance, Heart Rate and Sleep

How accurate is Apple Watch?

A 2020 review found that the Apple Watch was highly accurate as a fitness tracker when measuring daily step counts, especially at moderate intensity levels. However, this accuracy varied, with the device overestimating at slower walking speeds and underestimating at faster ones. The review also found that the Apple Watch overestimated energy expenditure. Although formal research from that 2019 study was not made available for heart rates in healthy subjects, researchers found that in patients with cardiovascular disease, Apple Watch HR was accurate during exercise. This work showed promise for its potential use in HR-guided training programs for cardiac rehabilitation. Additionally, according to a 2021 report by Apple, watchOS 7 and later models allow users to note if they are taking heart rate-limiting medications, which modifies the algorithm used to calculate VO2 max, providing more accurate results.

Follows closely:Steps, heart rate and VO2 max

Does not track accurately: Energy expenditure and speed

How accurate is the Oura ring?

The Oura ring excels at tracking sleep, nightly heart rate, and body temperature, offering insight into readiness and overall well-being. This 2024 study published in Journal of Clinical Sleep Medicine It serves as a testament to Oura’s sleep measurements, as it performed impressively well alongside medical-grade sleep studies. A 2020 study suggests that it also does a great job of reading nighttime heart health metrics, but little research has been done to assess its accuracy during the day. However, research suggests that when it comes to step counting and energy expenditure, it may be suboptimal. In 2023, that study found that while it can detect large changes in energy expenditure, it becomes less sensitive as activity intensity increases. The ring struggles to count steps due to its location on the finger, often confusing hand movements with steps. Additionally, without GPS, it can’t accurately track distance or speed unless paired with a phone. Oura rings also track VO2 max, but Oura’s blog post explains that this is a “broad estimate” and won’t be as accurate as lab measurements.

Follows closely:Sleep, nocturnal heart rate variability and heart rate, body temperature

Doesn’t track accurately:Steps, distance, speed

How accurate is a Withings watch?

A recent study found a strong correlation between estimated steps from Withings watches and those obtained using devices that are widely considered the gold standard for estimating steps and activity. Additionally, Withings tended to estimate relative energy expenditure levels with exceptional accuracy. Similarly, recent research suggests that while Withings demonstrated acceptable HR accuracy for general consumer use, it may not be suitable for situations requiring more precise HR measurements, such as healthcare or clinical research. Notably, Withings demonstrated lower HR accuracy during mobile activities such as walking, gardening, and housework, compared to more sedentary activities such as desk work, eating or drinking, and sitting. According to Withings, the ScanWatch measures VO2 max, however, there are no published studies on its accuracy, so it’s safe to assume it’s not medical grade.

Follows closely:Energy expenditure, heart rate (sedentary) and steps

Doesn’t track accurately: Heart rate (mobile)

We return to the age-old question: How accurate are fitness trackers?

In short, they’re not always accurate, but they point us in the right direction. The compilation of studies further promotes the narrative that people should treat these fitness trackers as tools that give them relative information about our overall health. Instead of focusing too much on individual metrics, they should step back and focus on overall trends.

Health apps can help people visualize and identify patterns in the information their device tracks around the clock, helping them make more informed health decisions.

While this may not be the answer you wanted to hear, fear not! This doesn’t mean you should stop trying to reach 10,000 steps per day or ignore these metrics altogether. It just suggests that it’s a good idea to avoid basing lifestyle and health decisions solely on these numbers.

This story was produced by Guava Health and reviewed and distributed by Stacker Media.