I ran 30 miles with 5 smart watches. This is the one you can actually trust

Key points to remember:

• All five watches accurately tracked steps and distance, but heart rate accuracy varied.
• The Apple Watch Series 11 was the most accurate heart rate monitor during workouts.
• The Garmin Venu 4’s heart rate tracking contains more data, ideal for serious workout analysis.
• If steps and distance accuracy are your priorities, you don’t need an expensive smartwatch.

I didn’t have a goal of running a marathon when I started this project. Testing the accuracy of smartwatches felt more like a few leisurely jogs, with a few watches stacked on my wrists. I’ve tested dozens of smartwatches over the years, but never five at once, and never under the level of scrutiny this test demands. Mile after mile, I pushed my heart rate (and my body) well beyond my comfort zone, with the finish line on point.

Fitness trackers have come a long way since the early days of step counting at Fitbit, and in today’s wearable landscape, a reliable step counter isn’t enough. Smartwatches, rings, fitness bands, and even headphones compete for space on your body to monitor everything from heart rate to temperature. To get ahead of the competition, they need to be accurate enough to detect subtle changes in your vital signs and turn that data into results.

I tested five models (one at a time), ranging from $80 to $550, to determine which was the most accurate in terms of steps, distance, and heart rate. Heart rate, in particular, is the most critical (and hardest to obtain), as many other metrics depend on it.

It’s not like I’m starting from scratch. I had already tested the Samsung Galaxy Watch 8, the Google Pixel Watch 4, the Garmin Venu 4, the Apple Watch Series 11 and the Amazfit Bip 6, and each had proven itself in its category. There’s a reason they landed on our best lists. But taking a look at a training summary and dissecting raw data are entirely different beasts.

After two months and over 30 miles of testing, I’m finally ready to share the results (and give my legs a rest). The biggest takeaway: All five watches performed well in real-world testing. None deviated by more than a few percentage points from the control when measuring steps and distance.

Heart rate accuracy was found to be the biggest differentiator. On the surface, the watches looked similar: average and maximum heart rates were often only a few beats apart. But the discrepancies became evident in the second-by-second data. While most stayed within 8% of our control, the Apple Watch Series 11 stayed within 1% of our control’s Polar H10 chest strap, earning it the award. CNET Labs Awards for the most accurate heart rate monitoring possible.

The Garmin Venu 4 came in second, recording heart rate every second, compared to every 5 seconds on the Apple Watch. For most people, this level of granularity is excessive, but for serious athletes who rely on second-by-second feedback, this could be the deciding factor.

Heart rate: electrodes vs optical sensors

Heart rate is one of the most important vital metrics tracked by your smartwatch because it powers many other metrics, such as calories burned, intensity, heart rate variability (a measure of the variation in time between heartbeats), and VO2 max (the maximum amount of oxygen your body uses during exercise). As a casual fitness enthusiast, I regularly use live heart rate data from my watch to make runs and strength training workouts more intense.

Most smartwatches, including the five we tested, take heart rate measurements in the background at regular intervals throughout the day. However, they increase the sampling frequency during exercise. Even a short training session can generate hundreds of additional data points compared to passive tracking alone.

CNET’s heart rate test

To capture a wide range of heart rate data, I tested each watch individually on three separate 1-mile runs on a flat track. I maintained a moderate intensity for the first half of the race (around zones 3-4), then went all out for the second half, pushing myself as close to my peak as possible (zone 5).

I cleaned the sensors and secured each watch securely (about one to two fingers below the wrist bone) before each run. Each watch was tested one by one with a Polar H10 chest strap, CNET’s top-rated consumer heart rate monitor. Unlike optical sensors on the wrist, which detect changes in blood flow using light, chest straps like Polar’s use electrodes to directly measure electrical signals from the heart. Due to this method and proximity to the heart, chest straps are widely considered more accurate than wrist-based devices. Ensuring this level of precision is not realistic for a watch, but they come close.

During testing, I noticed a consistent trend: Most watches lagged behind the chest strap during the first minute of a run, when heart rate increased rapidly from rest. Once I reached cruising altitude (zones 3 and 4), the readings aligned more closely. But when I entered zone 5, differences reappeared, with some watches struggling to keep up during peaks above 160 beats per minute. The Bip 6, for example, never recorded my maximum heart rate. This discrepancy explains why training summaries often look the same. Average and maximum heart rates were just a few beats away from the chest girdle, while second-by-second analysis revealed significantly larger deviations.

Since raw second-by-second heart rate data isn’t easily accessible in most applications and can include thousands of data points, I teamed up with Gianmarco Chumbe, CNET’s senior lab engineer, to interpret and map the results. The graph above shows how close the Apple Watch Series 11 was to the Polar chest strap, with an error rate of less than 1% (an average of 1.4 bpm across all three tests). In our results, it ran almost side by side throughout the analysis, even on the outer edges of the graph, where the other watches struggled. This consistency earned it our Labs Award for Most Accurate Heart Rate Tracking. There is, however, an important nuance.

The Apple Watch data we pulled (via the HealthFit app pulled from Apple Health) sampled heart rate approximately every five seconds. In comparison, the Polar chest strap and the Garmin Venu 4 recorded data almost every second. Of the data points we were able to compare, the Apple Watch was closest to the chest strap, but it had fewer data points. The Venu 4 matched the chest strap sampling rate, but with a slightly higher error rate of 3.89% (5.5 bpm). These extra seconds of data could help guide training decisions and, over time, mean the difference between finishing strong and setting a new personal best.

All watches have heart rate error rates below 8%, which is impressive, especially at higher intensity levels. It should be noted that these were short workouts (8-9 minutes per run). Since the Google Pixel Watch (5.6% error rate) and Samsung Galaxy Watch (6.6%) tended to catch up with the chest strap over time, longer runs would likely reduce some of these gaps. The Amazfit showed a similar overall error rate (7%), but struggled to capture the highest heart rate peaks. This limitation makes it less ideal for prioritizing heart rate accuracy during intense workouts.

After over 30 miles of testing, I’m more convinced than ever that heart rate accuracy actually has an impact on training. In six weeks, my VO2 max went from 41.3 to 45.8, according to Apple Health. I haven’t reached this level since my third pregnancy, three years ago. Without the watches and the chest strap as a guide, I might not have recognized what “pushing myself” really meant in the moment.

Remote test CNET

Measuring the distance turned out to be much easier, both physically and technically. Distance accuracy is important because it also feeds into other metrics, such as pace, calories burned, and training load (the duration and intensity of exercise over a specific period of time).

The most reliable way to test distance was to follow a route with precise measurements and minimal elevation change. (Credit goes to Gianmarco for suggesting a track test.) Most high school and college tracks are built to official specifications: 400 yards per lap. I found an old college trail near my house that had been paved, but was still within the regulation length. I even broke a measuring wheel to be sure. I ran every test on this track, reliving the high school day 30 times, but with more knee pain.

Although GPS is a major factor in outdoor tracking, distance is also calculated using data from an accelerometer and motion sensor. To control the variables, I put the phone paired with the watch into airplane mode before each run to prevent it from using GPS. I photographed each watch display after each lap (in 400m increments) to capture a data point, repeating the process four times (1600m is just over a mile).

All five watches were within a tenth of the actual distance, which is an incredibly close gap. The Apple Watch again led the pack, measuring my runs at 0.99 miles for all three tests. The runner-up was the Garmin Venu 4, which averaged 0.96 miles per test (just 0.03 miles behind the Apple Watch).

Accurate distance tracking isn’t just for high-price tags. The $80 Amazfit Bip 6 averaged 0.95 miles per test, proving it’s more than capable for walkers or casual joggers looking to log miles.

CNET’s milestone test

Once considered the holy grail of fitness tracking, step counts have slipped down the metric hierarchy as more advanced health markers have taken center stage. And while the 10,000 step goal is somewhat arbitrary, it sets a goal and gets people moving.

Today we know that reaching a specific number of steps is less important than walking and progressing over time. The steps remain an accessible starting point for many people and their accuracy is important. The “extra credit” from a faulty tracker can lull people into sleep and give them a false sense of accomplishment. And if a device fails to master the basics, it raises questions about the rest of its measurements.

While pedometers were once considered the gold standard in this category, a $10 model today is likely less accurate than the smartwatches on this list. Traditional pedometers use a simple mechanical switch triggered by hip movement, while most modern smartwatches use accelerometers and motion sensors to detect and measure movement in multiple directions.

To test the accuracy, I went old school and counted each step myself with a hand counter (like the one you use for baseball). I also used StepsApp, a pedometer app on my phone, as a backup. I started with 1,000 steps for each watch on a flat path. I didn’t use the track, but I didn’t follow the exact same route for each test, which may introduce minor variations.

The results were incredibly close; all about 10 clicker steps away. The Galaxy Watch 8 results (18 steps) were the exception, but I suspected that might be a fluke. So I retested and raised the stakes; this time, taking 2,500 steps with each watch. The results were almost identical. None differed by more than 11 levels, or less than half a percentage point.

The differences were negligible, so all watches were winners in this category, proving that there’s no need to splurge for accuracy. This Amazfit Bip 6 looks pretty fantastic right now.

Twists and variables to consider when tracking workouts

Even with the best intentions, 30 miles of testing, and a data scientist on my side, there’s no way to eliminate all variables in real-world conditions. These results are not gospel. They’re rigorous, rehearsed, and carefully averaged, but they’re still human and your mileage may vary (pun intended).

It took me over 30 miles of testing before I felt comfortable putting the results on paper, as I was constantly encountering back and forth. laughable, especially for heart rate.

The order of the tests was important. The first watch of each session was always at a disadvantage as my heart rate started to drop and increased more dramatically. By the second and third runs – even with deliberate rest periods to bring my heart rate down – the jump wasn’t as clear. Your body doesn’t completely reset as quickly.

To mitigate this, I rotated the starting watch for each session. I limited each outing to three runs (three miles total), making sure each device had the opportunity to be tested first, middle, and last. Our lab data and results (on the story graphs) are averages of the error rates on these three tests.

Sensor fit and interference were other issues. The sleeve of my jacket sometimes made the watch move; warmer days meant more sweat at mile three, which can interfere with optical readings, and then there was the time I almost cut off my circulation by wearing the Galaxy Watch too tightly.

The Data Extraction Nightmare

Then came the data. Raw heart rate data from Polar can be downloaded as a .CSV (spreadsheet) file ready for analysis.

Garmin’s is almost as simple, provided you have a data analyst and a Reddit thread. It can export workout-specific heart rate data as a .TCX file, which was foreign to me. Gianmarco wrote custom code, based on information found on Reddit, to extract and convert the data into a format corresponding to Polar’s output. Amazfit required a similar conversion process.

Apple, Google and Samsung made us work for this. All three require exporting your entire health records (and I mean everything, not just workouts or heart rate). For me, that meant downloading over a decade of health data. Once extracted, the compressed file opens into a maze of nested folders with cryptic labels. The best strategy is to sort by date and hope that one of the files mentions heart rate.

For Google I got lucky and found the right file after hours of searching. For Apple, several third-party applications are available and can do the sorting for you. I downloaded the $6 HealthFit app, which filters and pulls data directly from the Health app. However, the sampling rate was not as dense as the Polar bracelet, leaving fewer data points to compare. It’s hard to say if it would have been different if I could have pulled it directly from the Health app.

With Samsung, the only feasible option was to use the Strava app as an intermediary. I started the workouts in the Strava Watch app and exported the data to the desktop version. This all took two people several hours over several days to figure out. Accessing your own health data shouldn’t be that difficult.

Bottom Line of Smart Watch Accuracy

If your heart rate accuracy is your top priority, the $400 Apple Watch Series 11 is what to buy. He was the all-around winner, consistently performing well in all categories and the most accurate in terms of heart rate, staying within 1% of the chest girdle during races.

But the takeaway after 30 miles of testing is that you can’t go wrong with any of these watches; it just depends on what you value most.

The $550 Garmin Venu 4 may be better suited for data enthusiasts and serious athletes. It’s Gianmarco’s choice: “The combination of high-fidelity and export-friendly access makes it particularly attractive to users like me, who want full visibility into their training data.”

It’s also the best option for Android phone owners wanting elite-level heart rate tracking.

The Pixel Watch 4 and Galaxy Watch 8 (both $350) are reliable for steps, distance, and overall heart rate trends. You might not get the same second-to-second accuracy during intervals, but for everyday workouts, they’re more than capable. And the Amazfit Bip 6 is a reminder that accurate distance tracking doesn’t have to be expensive. For beginners looking to build a baseline without a major investment, it’s better than its $80 price suggests.