How Does Fitbit Work to Track Daily Activities?

Fitbit is a well-known brand that creates smartwatches and fitness trackers capable of monitoring various activities. These activities include heart rate, blood oxygen levels, steps, distances, calories burned, and breathing rate. However, many people wonder how Fitbit calculates all of these activities. How Fitbit watches work is quite simple. They track, calculate, and determine readings for your sleep, steps, distances covered, stress, calories, and floors climbed. Continue reading to find out how Fitbit Watches work!

How Does Fitbit Work to Track;


For those wondering whether Fitbit can track sleep, the answer is yes, it can. Fitbit watches detect or know you are asleep when they detect you’ve been still (haven’t moved) for at least an hour. 

The watch sends the movement and heart data to the Fitbit app on your paired phone, where they are combined to create your sleep report, including sleep stages. 

Fitbit also provides sleep scores. To determine your sleep score, Fitbit combines three sets of data: your sleep stages, heart rate, and the time spent restless or awake. On the other hand, sleep stages (light, REM, and deep) are also monitored using movement and heart rate data.


You are recommended to take at least 10,000 steps daily, and Fitbit watches can help you track your progress toward this goal. But how does step tracking on Fitbit work? Well, to track the number of steps you have taken throughout the day, Fitbit uses a built-in 3-axis accelerometer, which measures acceleration forces, including data such as distance covered, floors climbed, and calories burned. One of the reasons I like Fitbit watches is that they calculate steps accurately; therefore, the step count on Fitbit is data you can trust.


Fitbit watches can determine the distance covered by walking and running. To measure the distances you’ve traveled Fitbit uses your steps, the length of your strides. Hence the formula; Distance Traveled = Steps x Stride Length!

Floor Climb

If you live in an apartment and usually take the stairs instead of the lift, you may want to track the number of floors you climb in a week or month. You can do this by getting yourself a Fitbit tracker like the Versa 4, Sense 2, or Charge 6. All Fitbit watches determine floors climb the same way. To know how many floors you have climbed, Fitbit watches use their onboard altimeter sensors, which are responsible for tracking when you elevate. The elevation report is combined with your steps and barometric pressure data to determine the total number of floors you have climbed. Please note that 3 meters or 10 feet on Fitbit represents a single floor. Also, Fitbit doesn’t record steps down the stairs and treadmills as floors climb.

Calories Burned

Fitbit is one of the best watches to consider when you want to lose weight or keep your body in check. This is because it can calculate the calories you’ve burned throughout the day. You can always trust the calorie report you see on Fitbit because it is close to what’s been provided by verified calorie counters. It is very simple how Fitbit watches track calories burned; to determine the number of calories you have burned, Fitbit combines BMR (Basal Metabolic Rate) with your activity report.

Heart Rate or Heartbeat

Fitbit watches like Charge, Versa, Sense, Luxe, and Inspire can help you keep an eye on your health. To determine your heart rate, Fitbit shines a green light on your skin, and since your blood absorbs light, detectors known as photodiodes calculate how much light the blood has absorbed. The heart rate readings you see on your Fitbit watch are a result of the rise and fall of the lights being absorbed by the blood. Unfortunately, the heartbeat or heart rate data you see on Fitbit is not 100% accurate. Therefore, you should treat the data as a clue for your heart. If you want accurate heart rate readings, visit a medical professional or use a verified monitor.

SpO2 or Blood Oxygen Levels

Apart from your heart rate, the Fitbit watch can determine how much oxygen is in your blood. However, you can’t rely on the readings because they correspond with the readings provided by medical equipment. Only use the SpO2 readings on Fitbit as estimates for your blood oxygen saturation. That said, Fitbit calculates SpO2, or blood oxygen saturation, by shining lights (red and infrared) on your skin where they hit your blood vessels. The light bounces back, and Fitbit uses the light to estimate the levels of oxygen in your blood. More red light bounces when your blood is rich in oxygen, whereas more infrared light bounces when your blood is not richly oxygenated.

Breathing or Respiratory Rate

Did you know that most Fitbit watches, especially the recent models, can track and determine your breathing rate? By using your heart rate, Fitbit can calculate your respiratory rate. Here’s how it works: Fitbit interprets that you are inhaling when your heartbeat decreases and exhaling when your heartbeat drops. The differences in the intervals of your breathing are then measured to determine your respiratory or breathing rate.


Another data that Fitbit watches can track is stress. Fitbit describes your stress using a score that ranges from 0 to 100. The higher your score is, the fewer signs of physical stress your body shows. A low score indicates you are less prepared for the day. Because of this, you may perform poorly in whatever you do throughout the day. To determine your stress levels, Fitbit combines the data collected by the EDA sensor with your skin temperature, heart rate variability, and heart rate data.

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Jashon Kanaiza

I’m Jashon Kanaiza, a lover of life, books, gadgets, and coffee. I spend hours testing, researching, reviewing, and troubleshooting wearable tech by an array of brands. My goal with JayFinity is to help you push your wearable to its limit. From tips to how-to guides to reviews, you deserve the best wearable information – without a paywall behind it.

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