How Accurate Is Fitbit? The Truth About the Fitness Trackers

Trust is a privilege we can’t afford in an increasingly chaotic time. The line is said for living men and women, but have you ever wondered why we trust the devices we use? Without knowing the authenticity of the data, we rely on them.

Are smartphones and smartwatches reliable in terms of data?

If you haven’t thought about it, then this is high time to give it a thought.

These devices need to be accurate and precise to gain our trust. So obviously, you won’t want false data being poured into you.

Just imagine returning from a strenuous uphill run and returning home. As soon you return home, you lie down on your couch and start to wonder if the data you had been relying on is false all this time. If this thirst for knowledge has driven you to this page, give this article a read.

Today, we will clear all your ambiguities (not regarding life or its purpose, but Fitbit devices) of accuracy, as we will provide insight into whether the Fitbit devices are reliable at the job they do or are mere eyewashes.

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Step Counter on Fitbit

We are pretty much aware of the 10,000 steps mantra from health professionals who keep repeating the slogan for us to stay healthy.

“Walk for 10,000 steps daily to maintain a healthy body and a healthy mind”. This line has lured many of us into buying a supposedly accurate and precise fitness tracker from Fitbit.

Now the question arises on how the Fitbit devices keep track of our steps?

Fitbit devices come with built-in hardware, i.e., the accelerometer, which detects motion. The advanced devices come with a 3-axis accelerometer. The 3-axis allows the device to notice the direction of movement, i.e., forward or backward. The device can distinguish between running and strolling too.

Having explained the working, now we move on to the reliability of the devices.

The watch uses complex algorithms to analyze the data from the hardware to reach conclusions.

According to a study carried out by Lynne et al. (2018), the Fitbit devices were likely to meet acceptable accuracy for step count approximately half the time.

A 50% accuracy is impressive, keeping in mind these results are strictly medical-based research. The difference in step counter is attributed to this gadget being worn on the wrist.

The wristband notices every movement of the hand instead of the feet. So if you don’t move your hands while walking, an undercount of the steps is seen. On the other hand, overcounting is encountered due to the wrist’s movement. This is because the device keeps adding steps to the counter even when sitting, working on your computer.

How To Make Your Steps More Accurate?

So, now we will help you out with the problems of steps recording.

  • The first issue addresses those people who do not move their hands while walking. For them, it’s better to cling the device to your clothing while walking. Instead of wearing the device, you can cling it onto your hip to attain more precision.
  • Provide accurate personal data. This includes height, weight, gender, and stride length data. The watch calculates your number of steps and the calories burned based on this provided data. The exact value will help reduce the abnormalities in the calculation.
  • Remove the tracker while carrying out hectic hand activities. For example, playing drums, directing an orchestra, or kneading bread adds to the steps counter to your hand movements. Thus, disrupting the actual steps. So, it is better to remove the watch before executing these activities.
  • Secure fastening of the band to the wrist should be ensured. A loose band or one attached to a bangle can alter the results.
  • Please keep your eyes open for updates, as they contain fixes and algorithm improvements.
  • Another critical step is determining which wrist the watch should be worn. The dominant wrist setting decreases the sensitivity of step counting. Your dominant hand is used for most daily tasks, such as eating and writing, etc. the non-dominant hand increases the sensitivity. It is recommended that you wear the device on your non-dominant hand to reduce the potential extra steps from arm movements. 


When the laboratory-made measuring equipment was tested, errors were also found in the devices. So, we conclude that the pedometer is reasonable compared to other trackers in the market but still lags behind the true medical equipment.


Fitbit’s Accuracy In Measuring Calories Burned

Obesity is plaguing the global population. But, whenever an obese visits the doctor, all he has to listen to is “Reduce your Calories,” and that too on a repeat button. So, counting the daily calorie intake is essential for many who seek a fitness tracker. Thus, knowing the authenticity of your calorie count is crucial.

To measure calories burned, an accurate medical device is used typically. For example, a Metabolic Analyzer composes a mouthpiece that counts the number of calories burned by noting changes in oxygen levels.

However, a Fitbit device calculates your Basal Metabolic Rate (BMR) to reach the calories burnt. A BMR is a measure of metabolism (energy-burning) of the body while you are sedentary. The very rate relies on your height, age, weight, and gender.

For some reason, the calorie counter on the trackers works fine when stationary. However, the trackers’ accuracy decreased as the people started moving in research. For example, the Fitbit device overestimated the energy expenditure in subjects who started to walk by an average of 16-40%. Astonishingly an underestimation was seen in household activities, which measured up to 27-34% below the required value.

Another research that used the Metabolic Analyzer and the Fitbit device (Fitbit Classic) side-by-side concluded abrupt measurements. For example, a lower than normal value was seen in activities such as walking and treadmill, while an overestimation was observed in carrying groceries.


Fitbit devices are not very accurate at measuring calories burned. Fitbit Flex is a considerable device with better results than others.


Fitbit’s Accuracy At Heart Rate Tracking

Here we’ll tell you how accurate Fitbit’s heart rate is?

Heart rate is a sensitive aspect, and fewer people exist who purchase fitness trackers for medical purposes. However, heart rate tracking is almost an essential feature of every Fitbit device, Fitbit Alta HR, Fitbit Versa series, Fitbit Charge HR series all comes with heart health monitoring.

In a medical setup, the doctors use an Electrocardiogram or an ECG machine to measure changes in the heart rate of the patients. The ECG machine presenting the heart rate on a sheet of paper is considered the most accurate measure.

On the other hand, a smartwatch uses an optical heart sensor that works on Photoplethysmography (PPG) principle. First, the device shines light onto the skin intended to penetrate the artery. Then, a heart rate measurement is done based on the amount of light reflected from the artery back to the device.

Research to find out the accuracy of smart devices in measuring heart rate was carried out that involved 50 healthy volunteers. The volunteers had ECG machines attached to them and wore smart devices. It was found out that the Fitbit HR was accurate 84 percent of the time. However, the accuracy started to fall around 100 beats per minute, and inconsistency increased with increasing heart rate.

The adverse effect of miscalculation

The adverse effect is that people rush to the medical professionals informing them that they have been working hard but cannot reach the required criteria based on the heart rate scores they obtain on the Fitbit devices. Instead of this pursuit, they can injure their heart.

Cause of miscalculation

PPG technology requires a stationary arm to measure the heart rate accurately. Hectic activity disrupts the device and alters the results.

The Fitbit Spokesperson has clarified that the devices are not meant to be used for medical purposes.


The Fitbit devices can measure your heart rate with accuracy when at complete rest, which means Restoring heart rate tracking is satisfactory. The Fitbit Charge HR is considered the best in measurement. However, when you start motion, such as during a workout, it is not recommended to rely on the results.

Fitbit Charge 2 Accuracy In Heart Rate Tracking

A study was carried out by Benedetto et al. (2018) to analyze the accuracy and precision of Fitbit Charge 2 in heart rate measurement. It involved 15 healthy participants who were asked to ride a bike (stationary bike) for 10 minutes.

The results showed an underestimation of heart rate measurement from the device. As per the study, an individual heart rate measure could plausibly be underestimated by almost 30 beats per minute.


The Fitbit Charge 2 gives poor precision for individual measurement, which could be underestimated by as much as 30 bpm. The irregularities can be attributed to the improper positioning of the device.

Fitbit Charge HR: Best Heart Rate Measurer

The Fitbit Charge HR is lined amongst the best heart rate measuring devices. It competes with the Fitbit Surge.

Accuracy of measurements

Fitbit found itself in hot waters when a company challenged the accuracy of the Fitbit HR. They claimed that the Charge HR was off by an average of 15.5 beats per minute (bpm). However, the claims were put to rest when a test by Consumer Reports was surfaced.

Charge HR: The Victorious One

The Consumers Report claimed that of the 64 heart rate measurements carried out by Fitbit Charge HR, the device gave similar results to the chest strap monitor.

Thus, the study concluded that the Fitbit Charge HR was highly accurate, and the difference accounted for no more than three beats per minute.

Fitbit Charge 3: Best Fitness Tracker

The Fitbit Charge 3 is considered the King of the smart trackers. Its excellent and accurate measurement has won many hearts.

Fitness tracking

It isn’t just an ornament instead of a complete package. The fitness features offered are beneficial and accurate to the core.

More than 15 sports modes are available. You can set and achieve goals in different modes, such as swimming, biking, yoga, etc. In addition, GPS integrates with fitness tracking and gives you accurate pace and distance data for outdoor workouts.

Health monitoring

Sleep monitor measures your REM and healthy sleep, while the continuous heart rate monitor is spot-on in measurements.

The watch proves to be an intelligent device by mapping out guided breathing sessions for you based on heart rate variations during the workout.


Fitbit Charge 3 is the best seller. Thus, its accuracy and precision are loved by the users.


Read More: Everything You Need to Know About the Fitbit Charge 5


How accurate are Fitbit devices at Sleep tracking?

According to scientists, a Sleep-driven man is worse than an intoxicated one. Sleep is an integral necessity to attain mental and physical health. In addition, a night of good sleep allows you to improve your overall health.

Insomnia is becoming a concern nowadays. Hence, many people are attracted to buying gadgets that shall help them monitor their sleep quality, Fitbit devices being one of those.

Fitbit uses Motion detectors and PurePulse heart monitors to analyze the quality and duration of sleep you get. The manufacturers claim that the devices can accurately measure the three stages of sleep, i.e., light sleep, deep sleep, and Rapid Eye Movement (REM) sleep stages.

Studies, however, point to a different story. Different studies conducted indicate that the devices are inaccurate in measuring sleep values. For example, the 2012 study found that Fitbit overestimated the sleep duration as it started counting Sleep-time while the subjects were awake.

In the wake of the scenario, a lawsuit was filed against the company in 2015, after which improvements can be expected.


The Fitbit is inaccurate at measuring sleep duration and quality both. Therefore, you should not rely on these results to measure your stress levels.

Based on user experience, we have listed some Fitbit devices that are accurate. However, it must be noted that these results are not laboratory-based trials. This just depends on the perception of users and holds no medical value.



Feehan, L. M., Geldman, J., Sayre, E. C., Park, C., Ezzat, A. M., Yoo, J. Y., … & Li, L. C. (2018). Accuracy of Fitbit devices: Systematic review and narrative syntheses of quantitative data. JMIR mHealth and uHealth6(8), e10527.

Benedetto, S., Caldato, C., Bazzan, E., Greenwood, D. C., Pensabene, V., &Actis, P. (2018). Assessment of the Fitbit Charge 2 for monitoring heart rate. PloS one13(2), e0192691.

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