What Is the Margin of Error on Fitness Trackers?

Most fitness trackers tend to have a margin of error of around 5-10% in step tracking. It also varies when it comes to heart rate and calorie burn.

Quality fitness trackers have a small margin of error. For instance, during an activity like walking up and down a set of stairs, reputable brands like Fitbit and Misfit boast 96.4% and 97.8% accuracy levels, respectively.

What about other brands, you wonder? Low-quality wearables often have several common features, including low-grade sensors and outdated technologies. As such, they are highly susceptible to higher margins of error. That is why we advise against purchasing the cheapest gadgets available in the market. It’s better to save up and get an excellent gadget.

In this article, we’ve discussed various aspects related to the accuracy of fitness trackers, including factors that may lead to inaccuracy. Is that something you’d like to find out? Read this piece till the end and pay close attention.

What’s a Typical Margin of Error for Step Counting?

Fitness Trackers Accuracy Stats

Fitness Trackers Accuracy Stats Infographic

Most fitness trackers tend to have a margin of error of around 5-10% when it comes to counting your steps. This means the step total displayed on your tracker could be off from your actual steps taken by about 5-10%.

For example, if your tracker shows you walked 10,000 steps for the day, your real step count was likely somewhere between 9,000 and 10,500 steps due to the margin of error. Typically, these devices slightly overestimate step counts. 

This 5-10% error margin is quite common across popular fitness bands and watches from brands like Fitbit, Garmin, Apple, and others when used for basic walking or running. The margin may be wider for other activities like cycling that involve less wrist motion.

How Accurate Is the Fitness Tracker?

Fitness Trackers Facts and Stats

Fitness Trackers Facts and Stats Infographic

Most reputable fitness trackers are reasonably accurate. By that, we mean that fitness enthusiasts can use them for various purposes, from monitoring heart rate and sleep quality to counting daily steps and lost calories.

With that in mind, several factors influence the accuracy of fitness trackers, including:

1. Tracking Methods and Algorithms

Fitness trackers rely on different tracking methods. For instance, although most wearables use MEMS accelerometers, the systems used are not always the same. Some products have piezoelectric MEMS accelerometers, while others come with capacitive components. Additionally, different algorithms are used in fitness trackers, ranging from peak detection to threshold-based algorithms.

Since different wearables come armed with different algorithms and tracking methods, they can’t have the same accuracy level. Ideally, the most accurate devices are the ones with the most refined of these technologies.

2. Installed Sensors

Fitness tracker sensors come in their varieties, from heart rate monitors and accelerometers to ambient temperature sensors and gyroscopes. Not all wearables have the same sensors. For instance, many Garmins have a barometric altimeter sensor, which isn’t common in Apple Watches.

Most importantly, top-quality fitness trackers have advanced sensors with optimized accuracy. On the other hand, since many manufacturers make a few sacrifices when it comes to cheaper wearables, they often come out with fewer low-quality sensors. And the latter are often plagued by inaccuracy issues.

3. Activity in Question

Fitness gadgets can track multiple activities. For instance, Fitbit Inspire 2 allows a wearer to keep up with 20 goal-based exercises, including running, swimming, weightlifting, and cycling. However, the activities have different degrees of accuracy.

Most wearables can track common activities walking on a treadmill astonishingly well. But when it comes to challenging activities like yoga, which involves controlled movements that are sometimes accompanied by minimal hand motions, these gadgets fail spectacularly.

4. Physiological Differences in Wearers

Did you know that your physiological traits can determine your fitness tracker’s degree of accuracy? Consider skin tone as an example. Several studies have proven that, when it comes to measuring heart rate, wearables are less accurate on darker-skinned people than those with a lighter skin tone.

The other element is age. Sage Journals argues that the step counts recorded by standard fitness bands can be inaccurate in older adults, who are associated with a shorter step width and a slower pace. That may be debatable, but it still raises a solid point.

To summarize, physiological differences like skin and texture can affect the accuracy of fitness trackers.

5. How and Where a Fitness Tracker is Worn

Most fitness trackers monitor arm movements using 3-axis accelerometers and translate them into data points, which come out as steps and activities. If you wear your smartwatch on your dominant hand, which you use more often, your gadget will register all movements, which can be a problem. For instance, you may wave at a colleague while sitting down, but your tracker might translate the hand movement into step counts.

How you wear a fitness tracker also determines its accuracy. For example, if you wear your gadget too loose and it keeps flopping around, it might falsely count the movements as steps. On the other hand, although wearing a smartwatch too tightly doesn’t necessarily lead to inaccuracy, it can lead to a beaver of problems, ranging from mild discomfort to poor sleep quality.

What Research Shows About Fitness Trackers and Accuracy

Accuracy matters big time if you want a gadget that truly helps you meet your fitness goals. You want real, reliable data to see your progress and push yourself further.

Some researchers recently did the legwork for us and published the findings at BMC Public Health. They tested four popular trackers – the Fitbit Flex, Withings Pulse, Jawbone Up24, abd Misfit Shine – to see how precisely they monitor your activity. 

So which trackers passed the test? Overall, the results were pretty solid. The trackers weren’t perfectly accurate, but they consistently got within a few steps or movements of the real counts. Close enough to give you a helpful picture of your workouts and daily movement.

The study found that users rated the Withings Pulse as the top fitness tracker overall based on satisfaction and ease of use. Out of the four devices tested, the Withings Pulse was the most precise and consistent at tracking steps and distance – the key measurements for fitness monitoring. This was followed closely by the Fitbit Flex, which also performed well for the accuracy and repeatability of step counting.  

The Jawbone Up24 and Misfit Shine scored lower on the accuracy and repeatability metrics. However, users gave the Misfit Shine high marks for its aesthetically pleasing hardware design, even though its tracking capability fell short of the Withings and Fitbit.

Experiments Devices Accuracy (%) Repeatability
Indoor Walking Straight Jawbone 97.7 0.55
Withings 99.9 0.86
Misfit 92.4 0.69
Fitbit 99.6 0.72
Walking Up/Down Stairs Jawbone 97 0.89
Withings 97.2 0.83
Misfit 97.8 0.79
Fitbit 96.4 0.81
Walking on Treadmill Jawbone 97 0.89
Withings 97.2 0.83
Misfit 97.8 0.79
Fitbit 96.4 0.81

Is My Fitbit Overestimating My Calories?

Do you suspect that your Fitbit might be overestimating your calories? We have some unfortunate news: it might be.

Fitbits are reasonably accurate at estimating burned calories. But, if you’ve been watching your gadget closely, you know it can only accurately detect calories burned when you are not moving. Once you get going, the accuracy drops. A recent study has supported this claim by showing that:

  • During walking activities, most Fitbits overestimate burned calories by 26-61%
  • During cycling, these gadgets underestimate burned calories by 37-59%
  • During jogging, they overestimate burned calories by 25-39%

Additionally, according to a different study, during weightlifting, most Fitbits overestimate burned calories by 12-48%.

But there are several tips you can use to boost the accuracy of your Fitbit’s calorie burn counter. Start by wearing your gadget on your non-dominant wrist and keep it snug, not too loose or too tight. Moreover, update your weight frequently to ensure your wearable has the right measurements.

Final Thoughts

No fitness tracker is 100% accurate. Even the best gadgets are susceptible to inaccuracy issues. That said, quality wearables are accurate enough to serve you well. Also, although the degree of accuracy may vary depending on factors like the activity being measured and the algorithm used, the results shouldn’t be off by a large margin.

Don’t start smiling yet. What we’ve said earlier only applies to quality fitness trackers. But the opposite is true for low-grade products. So, before purchasing and using any gadget, check if it’s from an established brand and review its online reputation. That will save you a lot of headaches. 

Common Questions

What is meant by “margin of error” for fitness trackers?

The margin of error refers to the potential difference between the measurements from your fitness tracker and your actual numbers. It accounts for the small inaccuracies in tracking.

Does the margin of error vary between different activities?

Yes, the margin can be higher for some activities. Cycling and elliptical training often have higher error rates around 10-15% due to less arm motion. Weightlifting also sees bigger errors due to limited wrist movement.

What causes variability in the margin of error?

Factors like tracker placement, skin type, movement patterns, and device algorithms can all impact accuracy. Optical heart rate sensors are less accurate with darker skin or tattoos. Side-to-side motion causes more error than forward-backward. 

How can I get more accurate measurements?

Calibrate your device to your stride length for better distance and step accuracy. Ensure proper fit – not too loose or tight. Use the right tracking mode for your exercise. Stay still briefly before recording.

Should I only look at trends rather than exact numbers?

Yes, focus more on the trends over time to account for error margins. Don’t get hung up on day-to-day fluctuations and exact figures. Consistent overall trends matter more.

How frequently are the error rates improving?

Margin of error on step counting has improved from about 15-20% to 5-10% over the last 5-10 years due to better sensors and algorithms. Accuracy continues to incrementally improve.