Fitness trackers do a lot more than count steps. Here at PCMag, we take many factors into account in our reviews, including accuracy, features, and style. This helps us determine the strongest options at every price level, as well which models make the cut for our list of the best fitness trackers. For a better understanding of how and why we perform our tests, this is what we look for when making an evaluation.
Design and Comfort
It doesn't matter how accurate a fitness tracker is if it's just going to collect dust at the bottom of a dresser drawer. That means you should get a tracker you actually want to wear. Everyone has different taste when it comes to fashion, so we're not looking for a single design that will make everyone happy. We are, however, looking for versatility. Trackers that let you adjust straps score extra points, as you can dress them up formal events or dress them down for the gym.
Comfort matters, too. If you're not planning to track sleep, then a tracker should at least be comfortable enough to wear for the majority of the day that you're awake. To test this, we wear trackers every day for at about a week (or longer if time permits). We wear them in the shower if they're water resistant, while running errands, in the office, at the gym, and to bed if they track sleep.
After reaching a full charge, we wear each tracker until the battery dies and note how long it lasted. If text, call, and app notifications are available, we turn them on. Once the battery is drained, we'll charge it up to 100 percent again, this time measuring how long it takes to recharge.
Many factors impact battery life. While some trackers won't last more than a day or two, others can go weeks or even months (in which case we usually quote the manufacturer's battery estimate). A general rule of thumb is that the more advanced the device, the shorter it lasts. Color touch screens, continuous optical heart rate monitoring, and built-in GPS can all be significant drains on battery, all of which we take into consideration. For example, while three or four days on a single charge might not seem impressive, it is if the tracker has all of those advanced features.
Sensors and Smartwatch Features
In addition to the sensors mentioned above, there are a number of others we look for when evaluating new trackers. And with many new smartwatches shipping with fitness-focused features, the lines are blurrier than ever.
The most basic trackers include a three-axis accelerometer, which measures steps and distance traveled. To measure heart rate, manufacturers generally opt for an optical sensor (the green flashing light you usually see on the other side of the display). Some trackers may include barometers and altimeters to measure elevation, as well as GPS. Bluetooth is pretty much a given, but you might find a cellular modem for standalone LTE support.
The more sensors you have, the less likely you are to need your phone nearby. Some smartwatch-tracker hybrids even come with the option to store and stream music directly on the device itself, which means you can leave your phone at home.
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When it comes to measuring accuracy, we focus on steps, distance, and heart rate, as these are metrics that are both verifiable and can be uniformly tested. We don't test active minutes, calories burned, and stairs climbed for a few reasons. Most manufacturers have their own definition of active minutes, making it difficult to judge. Calories burned is virtually impossible for us to verify as it depends on an app's algorithm and your own individual metabolism. And stairs or elevation climbed can vary widely depending on your individual gait.
For steps, we perform controlled tests on a treadmill for both walking and running. We opt for treadmills as speed influences your stride and can be kept constant throughout a workout. In each test, we wear the tracker being tested, a comparable competitor, and a control pedometer, the Yamax SW-200 Digi-Walker. The Yamax is a clip-on pedometer frequently used in clinical trials to test accuracy.
First, we do a one-mile walk at 3.5 miles per hour (roughly 17 minutes), which is the average walking pace according to various studies. Then, we do a one-mile run at 5mph (12 minutes). After each test, we record the number of steps and distance logged by the tracker. Once testing is complete, we calculate the percentage of difference for each test. Generally, trackers fall within a two to five percent range of the Yamax. In cases where we receive abnormal results, we will perform another test to make sure the data is accurate.
When it comes to distance, our tests depend on whether a tracker has GPS. If it does, we will turn on exercise tracking for a set, measurable distance outside. (For instance, Prospect Park in Brooklyn, NY, has a designated runner's lane with distances marked at every quarter mile.) If it doesn't, we will compare results from the one-mile indoor treadmill tests and calculate the percentage of difference.
For heart rate, we'll exercise while wearing both the tracker and a Polar H10 chest strap. During the workout, we'll do several spot checks to see how the numbers correspond, especially during warm up and cool down. Because chest straps use electrical signals to measure your heart rate, they tend to be more accurate than their optical counterparts. As a result, optical heart rate monitors can sometimes lag a few beats per minute behind. We find an acceptable margin of error to be five to ten bpm.
Sleep tracking can be a little trickier to test, and our results are largely based on comparing our perceived sleep times with those recorded by the tracker.
Beyond the Wrist
Our test methods most directly apply to wrist-based trackers. But by and large, the process remains unchanged for hearables (trackers worn in your ears, like the JBL UA Sport Wireless Heart Rate), or other form factors like the Motiv Ring.
Ultimately, the best fitness tracker for you comes down to your budget, health goals, and activity levels. To learn more, check out our roundups of best overall fitness trackers linked above, as well as the best options for runners and swimmers.
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