How Do Fitness Trackers Work? Your Questions Answered


It’s a question almost every runner and fitness buff has asked at some point… How do fitness trackers work? They’re not some magical device but a clever piece of technology that’s changed the fitness world as we know it.

Here’s a quick overview of how they work, their benefits, and some tips for using one.

What Are Fitness Trackers?

Fitness trackers are wearables, most often designed to be strapped around your wrist, but also come in clip-on devices, ring, or even necklaces. They aim to gather data about your activity and lifestyle using built-in sensors.

How Do Fitness Trackers Work?

Fitness trackers may look small and unassuming, but they’re genius technological gadgets. Here’s a quick insight into how they work.


Fitness trackers work mainly on sensors. These may include heart rate monitors, gyroscopes, and accelerometers – some have a temperature sensor.

These sensors detect all kinds of movement—forward, backward, up, down, twisting, twirling… This is how exercise intensity, heart rate, and other health metrics are measured.


Once the sensors have gathered data, it’s processed through an algorithm, translating it into something meaningful for us humans. Every fitness tracker has its own unique algorithm, but they all strive for accuracy.

Data Collection

The data is collected and stored either on the device’s memory or on the cloud, usually via an app that syncs to your phone. This allows you to go back and compare with it at any point.


Most fitness trackers have small, basic, but easy-to-use displays. If you want to eyeball your data nicely, check it out in the accompanying phone app so you don’t have to strain your eyes! You may be able to customize what you put on this screen.


Fitness trackers sync to apps or computers via Wi-Fi or Bluetooth. From here, they transfer over any necessary information, freeing up space so you can carry on working out.

Key Features of Fitness Trackers

Here’s some of what you can expect when investing in a fitness tracker.

Activity Monitoring (Steps, Distance, Calories Burned)

Monitoring your daily activity can be an eye-opener for some. They cover things like steps taken, distance covered, floors climbed, and calories burned, which is all invaluable information for those looking to make positive lifestyle changes.

Heart Rate Monitoring

Real-time heart rate monitoring makes it easy to train in your target HR zone. Plus, it helps monitor your heart rate, as you may spot something abnormal early and check it out before it becomes a problem.

Sleep Tracking

Understanding your sleep is extremely useful. You’ll start to notice patterns in sleep duration, sleep quality, and sleep stages. You can also start linking bad nights with potential causes from the day before, especially if you’re tracking your food.

GPS Tracking

Not all fitness trackers have GPS built-in, but the more advanced ones do. These devices can track your route if you’re doing something like cycling or running outdoors.

The advantage is that they are much more accurate than non-GPS trackers. You’ll get better real-time and post-activity information.

How Accurate Are Fitness Trackers?

Fitness trackers are more accurate now than they’ve ever been. They’re not the most precise devices on the market, but in most cases, they’re accurate enough to trust… Mostly. Keep in mind that the position you wear it in makes a difference too.

Also, remember that different types of data are more accurate than others. For example, step tracking is more accurate than a cardio fitness score. This is because tracking steps is simpler for a fitness tracker to do than calculate an overall fitness score.

Generally speaking, the further you get from actual data (steps, heart rate, exercise minutes), the more an algorithm is used to calculate fitness or sleep scores. These are essentially more complex algorithms that may or may not represent what they say they do.

How Do Fitness Trackers Know How Many Calories You Burn?

The calorie algorithm on a fitness track analyzes data from various sensors, including your age, weight, gender, activity level, and movement patterns. The device can calculate based on these numbers to suggest how many calories you may have burned during any exercise.

As we just mentioned, this falls into the “algorithm” category of information scores. It’s best to use this number as a baseline and not a hard and fast number.

How Do Fitness Trackers Know When You Sleep?

The various sensors on your fitness tracker monitor your movement, your heartbeat, respiratory rate, and sometimes skin temperature. These things all change when we sleep, so the sensors pick it up and can tell when we’re asleep versus awake.

Benefits of Using a Fitness Tracker

Whether you’re new to fitness or experienced but want an easy way to track your stats, here’s why using a fitness tracker is a good idea.

Motivation and Accountability

Your fitness tracker will remind you to stay on track with your goals throughout the day. Most of them have daily and weekly goals to hit, so you have milestones to work towards while building a healthier life in the process.

You can also set your own goals and track your progress as you work your way closer and closer to your goal. Seeing yourself get there is extremely rewarding!

Some fitness trackers also have a sharing function or a community, so others can see your stats. This can be great for accountability, keeping you on the straight and narrow.

Activity Awareness

Fitness trackers help bring awareness to your sedentary lifestyle. They help you to make a conscious effort to add more movement to your day, boosting health even more.

Goal Setting and Progress Tracking

Set goals that work for you. Activity level, steps taken per day, calories burned, distance traveled… You can pick yours. Then you can easily track your progress as you go, which is motivating as you see yourself getting closer and closer to each goal.

Heart Health Monitoring

Being able to monitor your heart rate often is valuable. While fitness trackers won’t necessarily tell you when something is wrong, a sudden increase in heart rate for no apparent reason or an unusual decrease are both causes for concern.

You can also train within your heart rate zones while working out. This is very handy and can help you to maximize your training effectiveness.

Sleep Improvement

By regularly monitoring your sleep patterns, you can pick up potential problems and interferences. For example, if drinking caffeine before bed disrupts your sleep, you can pick it up more easily if you take notes on what you ate or drank daily.

Use the sleep information to make better choices about exercise, meal choices, meal timing, and your sleep environment. It can lead to better rest!

Personalized Workouts

Some more advanced fitness trackers may offer personal workout recommendations. This isn’t often seen on the less advanced ones, but it’s a nice touch that more modern fitness trackers have.

Social Support and Competition

The ability to connect to social media platforms, share your workout stats, and join in challenges adds an element of fun. If you’re competitive, you can fight others for a spot on the leaderboard!

Do Fitness Trackers Connect With Other Apps?

Most fitness apps can connect to various 3rd party apps. In most cases, they’ll connect to health and fitness apps for tracking and training purposes. Most of these apps offer more metrics than the fitness tracker itself shows.

Some fitness trackers can also connect to calorie-counting apps, which can help you plan your nutrition and exercise together. You can also connect yours to a sleep analysis app for more in-depth sleep insights.

A few upmarket fitness trackers can connect to smart home systems, allowing you to control things like the lights and the temperature through your device.

Smartwatch vs. Fitness Tracker: What’s the Difference?

While most people these days have smartwatches, fitness trackers remain popular. Here are the biggest differences between the two so you can find out which one you have… And decide if it’s the best thing for you.


Fitness trackers focus only on tracking daily metrics related to health. You’ll get information like steps, distance, calories, sleep tracking, heart rate measurements, and sometimes specialized exercise profiles.

Smartwatches, on the other hand, are packed full of features. Aside from a comprehensive range of activity profiles and all the same measurement features a fitness tracker has, smartwatches also have things like messaging, music, and 3rd party payments.


Fitness trackers have smaller displays, although they’re usually pretty decent quality. The display is basic, showing only a few simple metrics. This is part of the reason they’re a little less in-your-face than smartwatches.

Smartwatches usually have larger displays and are more prominent on the wrist. Many of them come in color, and new watch faces can be downloaded, depending on what information you want to see on your home screen.


Fitness trackers are lightweight, streamlined, and small. Smartwatches are larger, bolder, and typically have more switchable band options and watch faces than fitness trackers.

Battery Life

As they don’t waste much battery on their screen or on notifications, the battery life on a fitness tracker is quite a bit higher than that of a smartwatch. Smartwatches tend to run out of battery faster, as their screens take up more processing power, they’re constantly communicating with your phone, and they have many more features.

Fitness trackers’ batteries can last for weeks before needing a charge. Most smartwatches need charging every few days to every week, although some brands—like COROS—have superb batteries that can last up to a month between charges.

Tips for Getting the Most Out of Your Fitness Tracker

Ready to take your training to the next level with your fitness tracker? Here’s how to use it most effectively.

Place Your Fitness Tracker Correctly

The heart rate sensor needs to be against your skin, on the top of your wrist. You should tighten it enough so the sensor is against your arm but not so much that you can’t slip a finger under the strap if necessary.

It should be placed about a finger’s width below the small bone that juts out on your wrist for best results. Try to place it in the same position every time you wear it.

Sync Your Tracker With Other Fitness Apps

For easier tracking and possibly more comprehensive metrics, pair your fitness tracker with other fitness apps you use. All your data will pull through so you can view your stats any time and compare to previous performances.

Make Sure You Update the Software

Continuing to use out-of-date software not only means that you probably won’t have the latest functionality, but you’ll also probably be more prone to problems, including being hacked.

Set the tracker to update the software automatically if you can. If not, set a reminder to check it every so often and make sure you’re up to date.

Keep the Heart Rate Sensor Clean

Sweat and dirt can leave a grimy film over the heart rate sensor, making it more difficult for the fitness tracker to measure your heart rate accurately.

Make sure you clean it regularly, and if your tracker is waterproof, you should occasionally shower with it for a deeper clean.

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Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.