How Do Fitness Trackers Measure Calories?

27 minutes read

Fitness trackers use various sensors and algorithms to estimate the number of calories burned during physical activities. These devices typically measure calories by incorporating the following components and techniques:

  1. Accelerometer: Fitness trackers contain an accelerometer, which tracks your body's movement in multiple directions. It measures the acceleration forces exerted on the device as you move. By calculating the frequency, intensity, and duration of your movements, the tracker estimates the energy expenditure associated with physical activity.
  2. Heart Rate Monitor: Many fitness trackers also include a heart rate monitor. They utilize an optical sensor or electrodes to measure your heart rate continuously. By combining heart rate data with body movement information, these devices provide more accurate estimates of calories burned during activities that involve different heart rate zones, such as high-intensity workouts.
  3. Basal Metabolic Rate (BMR): BMR refers to the number of calories your body burns at rest to maintain basic physiological functions, such as breathing and digestion. Fitness trackers often require information like age, gender, weight, and height to determine your BMR. This baseline metabolic rate is then used as a starting point for calculating the calories burned during activities.
  4. Machine Learning Algorithms: Fitness trackers employ sophisticated algorithms that consider a combination of sensor data, BMR, and user information to estimate calories burned. These algorithms continuously learn and improve over time. The more data the device collects, the better it becomes at predicting the energy expenditure associated with specific activities.


It is important to note that fitness trackers provide estimates rather than precise measurements of calorie burn. These estimates rely on statistical models and may have inherent inaccuracies due to variations in individual physiology, device limitations, and other factors. Nevertheless, they offer valuable insights and trends, helping users track their overall activity levels and make informed decisions about their exercise and lifestyle choices.

Best Fitness Trackers in 2024

1
Fitbit Inspire 3 Health & Fitness Tracker with Stress Management, Workout Intensity, Sleep Tracking, 24/7 Heart Rate and more, Midnight Zen/Black One Size (S & L Bands Included)

Rating is 5 out of 5

Fitbit Inspire 3 Health & Fitness Tracker with Stress Management, Workout Intensity, Sleep Tracking, 24/7 Heart Rate and more, Midnight Zen/Black One Size (S & L Bands Included)

  • Inspire 3 is the tracker that helps you find your energy, do what you love and feel your best. All you have to do is wear it.Operating temperature: 0° to 40°C
  • Move more: Daily Readiness Score(1), Active Zone Minutes, all-day activity tracking and 24/7 heart rate, 20+ exercise modes, automatic exercise tracking and reminders to move
  • Stress less: always-on wellness tracking, daily Stress Management Score, mindfulness sessions, relax breathing sessions, irregular heart rhythm notifications(2), SpO2(3), menstrual health tracking, resting heart rate and high/low heart rate notifications
  • Sleep better:  automatic sleep tracking, personalized Sleep Profile(1), daily detailed Sleep Score, smart wake vibrating alarm, sleep mode
  • Comfortably connected day and night: calls, texts & smartphone app notifications(4), color touchscreen with customizable clock faces, super lightweight and water resistant to 50 meters, up to 10 day battery life(5)
  • Includes a 6-month Premium membership complete with personalized insights, advanced analytics and more (New & returning Premium users only. Must activate trial within 60-days of device activation. Content and features may change)
2
Fitbit Luxe Fitness and Wellness Tracker with Stress Management, Sleep Tracking and 24/7 Heart Rate, One Size S L Bands Included, Lunar White/Soft Gold Stainless Steel, 1 Count

Rating is 4.9 out of 5

Fitbit Luxe Fitness and Wellness Tracker with Stress Management, Sleep Tracking and 24/7 Heart Rate, One Size S L Bands Included, Lunar White/Soft Gold Stainless Steel, 1 Count

  • See how jewelry gets smart with a tracker that doubles as a timeless accessory and features a vibrant color display. Apple iOS 15 or higher, Android OS 9 or higher .Operating temperature: -20° to 45°C
  • Get better sleep to power your days with sleep tracking and sleep Score in the Fitbit app
  • Feel a Buzz when you reach your target heart rate zones, while you earn active zone minutes
  • 6-month trial of Fitbit Premium(New and returning Premium members only. Must activate trial within 60-days of device activation. Requires valid payment method.Content and features may change. Terms & Conditions apply)
  • Maximize your exercise, understand resting heart rate trends and better estimate calorie burn with 24/7 heart rate tracking
  • Tune in to your body with health metrics like breathing rate, heart rate variability and more (in-app only)
  • Enjoy up to 5 days of battery without having to stop for a charge (varies with use and other factors)
  • Connect Luxe to your phone’s GPS & see real-time pace and distance on your wrist
3
Amazfit GTS 2 Mini Smart Watch for Men Android iPhone, Alexa Built-in, 14-Day Battery Life, Fitness Tracker with GPS & 70+ Sports Modes, Blood Oxygen Heart Rate Monitor, 5 ATM Water Resistant-Black

Rating is 4.8 out of 5

Amazfit GTS 2 Mini Smart Watch for Men Android iPhone, Alexa Built-in, 14-Day Battery Life, Fitness Tracker with GPS & 70+ Sports Modes, Blood Oxygen Heart Rate Monitor, 5 ATM Water Resistant-Black

  • 【BUILT IN AMAZON ALEXA & GPS】You can talk to Amazon Alexa on your Amazfit GTS 2 Mini Smart Watch. Ask questions, get translations, set alarms, and timers, create shopping lists, check the weather, control your smart home devices, and more. Get precise tracking on your daily steps, distance traveled, and calories burned thanks to integrated GPS..Water resistance depth:50 meters
  • 【14-DAY LONG-LASTING BATTERY】A fully-optimized battery management system provides upto 14 days of battery life for the Amazfit GTS 2 mini watch. Get rid of the anxiety brought on by constant charging, and keep the energy flowing. The 220mAh battery is ready to power you through upto two weeks of activity.
  • 【70plus SPORTS MODES & 5 ATM WATER RESISTANT】The Amazfit GTS 2 mini features over 70 built-in sports modes, allowing to cover sports enthusiasts whether indoors or outdoors. With 5 ATM water resistance, this fitness watch can resist any of your daily activities and can even be worn while swimming.
  • 【ALL-ROUND HEALTH MANAGEMENT】This smart watch can provide heart rate monitoring, blood-oxygen saturation measurement, sleep monitoring, stress level monitoring and female cycle tracking, as well as other functions to achieve total health management from your wrist. The PAI health assessment system also processes complex health data with an advanced algorithm to present your physical condition in a simple, single-value score.
  • 【SupR LIGHT AND THIN & BUILT IN AMOLED DISPLAY】The Amazfit GTS 2 mini adopts a borderless design. Featuring carefully curved 2.5D glass to enhance your most fashionable outfits. With a light 19.5 g weight, a thickness of 8.95 mm (without the sensor base), and a skin-friendly silicone strap, this smart watch allows you to enjoy the lightness of time. And a 1.55-inch vibrant AMOLED screen for enhanced color and clarity.
  • 【SMART NOTIFICATIONS & COMPATIBILITY】Get an intelligent little pal to remind you of the incoming calls, text messages, apps, and calendars, alarm clock, weather forecast, and suport control the music playback & camera on your smartphone. This smart watch can work seamlessly with iOS 10.0 & Android 5.0 or higher smart phones.
4
Fitness Tracker with Step Counter/Calories/Stopwatch, Activity Tracker, Health Tracker with Heart Rate Monitor, Sleep Tracker,1.10''AMOLED Touch Color Screen, Pedometer Watch for Women Men Kids

Rating is 4.7 out of 5

Fitness Tracker with Step Counter/Calories/Stopwatch, Activity Tracker, Health Tracker with Heart Rate Monitor, Sleep Tracker,1.10''AMOLED Touch Color Screen, Pedometer Watch for Women Men Kids

  • 🏃 【All-day Activity Tracking】Activity & fitness trackers track all day’s activity including daily steps, calorie consumed, workout distance and time, which help you achieve your fitness goals more efficiently. You can see detailed data on App "Keep Health".
  • 🏃 【1.10 inch AMOLED HD Touchscreen】 The durable stainless steel frame of C60 pairs flawlessly with the Skin-friendly fitness straps, while its 1.10 inch AMOLED HD Touch Color Screen design and multitude of invigorating watch faces blow you away any moment.
  • 🏃 【24/7 Heart Rate /Sleep Monitor】This fitness tracker can also monitor your heart rate and body temperature all the day. This fitness tracker supports real-time dynamic heart rate, blood oxygen, blood pressure, so you can know more about your physical condition.Track your time indeep Sleep, light Sleep, awake stage to better understand your sleep quality each night.The tracker analysis your sleep data and gives you a nightly sleep score in the app, to help you improving your sleep habits.
  • 🏃 【Smart Functions】An easy-to-use activity fitness tracker with various intelligent features. Including Call & Message Reminder,Remote Photograph, Drink Water Reminder, Sedentary Reminder, Female Health,Family Health, Alarm Clock, Stopwatch, Find Device, etc.
  • 🏃 【5 ATM Waterproof fitness watch 】Designed according to waterproof and dustproof standard, you can wear it when washing hands, taking bath, swimming, diving or getting caught in the rain will not damage your watch.
  • 🏃 【25 Professional Sport Modes】 This fitness tracker with 25 sports modes to track the corresponding exercise. It will record your workout time, heart rate, and distance.
  • 🏃 【Magnetic fast charging and Wide Compatibility】Regular use up to 10-14 days, standby for 30 days. C60 use magnetic fast charging provides better endurance experience.This watch is suitable for iPhone and android smartphone.Its durable, replaceable and washable strap with secure clasp is adjustable between mix 5.0in and max 9.45in, offering perfect fit for women, men and kids.
  • 🏃 【Loving Gift】Keep moving and maintain your health. It will be your gift with extraordinary wishes for your loved ones/friends/lover. Care about their physical condition and confirm their health status at any time. Everyone you love will understand your heart when they receive this gift.
5
Fitness Tracker Watch with Heart Rate Monitor, Large Screen Activity Tracker with Pedometer, Sleep Monitor, Calories & Step Counter, IP68 Waterproof Smart Watch for Women Men Fitness Watch for Sports

Rating is 4.6 out of 5

Fitness Tracker Watch with Heart Rate Monitor, Large Screen Activity Tracker with Pedometer, Sleep Monitor, Calories & Step Counter, IP68 Waterproof Smart Watch for Women Men Fitness Watch for Sports

  • Heart Rate and Sleep Monitoring: The Fitness Tracker monitors your heart rate automatically all day, and you can select manual mode through the App. The fitness Watch also monitors your sleep at night, providing a detailed analysis of your sleep quality (deep sleep, light sleep, awake time). It is a health advisor for women men in daily life.
  • Multi Sport Modes with Activity Tracking: The fitness tracker features 11 sport modes like running, walking and more. Additionally, the activity tracker records daily steps, calories burned, walking distance and active time throughout the day. You can also set a daily steps goals through the App to track your progress.
  • Smart Notification Reminder: You can get incoming calls, SMS messages, and SNS notifications directly on your wrist including Facebook, Twitter, Gmail ect. You won't miss any important calls and message and stay updated. Please note: the smart watch can not make calls or text.
  • Long Battery Life and IP68 Waterproof: This smart watch only requires 2 hours of charging and can be used for 5-7 days continuously. IP68 waterproof rating can withstand daily sweat, washing hands and rainy day, allowing you to fully enjoy your workouts.
  • More Functions & Compatibility: Fitness watch comes with multiple smart functions such as stopwatch, alarm clock, breathing guide and sedentary alert, enhancing convenience to your daily routine. The tracker is compatible with iPhone Android Phones which run on iOS 8.0 or Android OS 4.0 & Bluetooth 4.0 or above. Please note that it is not compatible with tablets or computers.
  • Reminders for You: The fitness tracker watch operates by touch button, NOT touch screen. To enhance your wearing comfort, please do not wear the watch too tightly to avoid excessive friction that may cause skin abrasion. Make your watch a rest after prolonged use.
6
Empower Your Lifestyle with Bluetooth Call Fitness Smartwatch for Women/Men, Alexa, Health and Sleep Tracker Smart Watch, Compatible Android iOS, Ideas Gift on Christmas, New Year, Thanksgiving Day

Rating is 4.5 out of 5

Empower Your Lifestyle with Bluetooth Call Fitness Smartwatch for Women/Men, Alexa, Health and Sleep Tracker Smart Watch, Compatible Android iOS, Ideas Gift on Christmas, New Year, Thanksgiving Day

  • ✅【Compatibility and Integration】The women's and men's smartwatches seamlessly integrate with other devices and applications. Compatibility with smartphone operating systems (iOS or Android) and the ability to make and answer calls, and receive notifications, and messages directly on the watch. Additionally, the smart watches are designed to withstand daily wear and tear and are resistant to water, making them suitable for various activities.
  • ✅【Advanced Health and Fitness Tracking】Smartwatches for women and men that offer comprehensive health and fitness tracking features, including heart rate and blood oxygen monitoring, sleep tracking, step counting, and workout tracking. Accurate and detailed data insights help us stay motivated and make informed decisions about our health and wellness.
  • ✅【7-Day Battery Life And Quick Charging】 Having a decent battery life is crucial for us to ensure that our multifunctional smartwatch lasts throughout the day without frequent recharging. Quican Bluetooth Smartwatch offers long battery life and has quick charging capabilities.
  • ✅【Customization and Style】Personalization options and over 100 watch faces, Available in 6 colors, and the straps are interchangeable (the strap fits 22 mm). Fitness smartwatches that allow us to customize the appearance to suit our style and preferences.
  • ✅【Customer Support and Return Policy】Having access to responsive customer support and a flexible return policy provides us with peace of mind. In the event of any issues with our waterproof bluetooth smartwatch, Quican is ready to assist and offer a hassle-free return process.
7
Fitbit Charge 4 Fitness and Activity Tracker with Built-in GPS, Heart Rate, Sleep & Swim Tracking, Black/Black, One Size (S &L Bands Included)

Rating is 4.4 out of 5

Fitbit Charge 4 Fitness and Activity Tracker with Built-in GPS, Heart Rate, Sleep & Swim Tracking, Black/Black, One Size (S &L Bands Included)

  • Use built-in GPS to see your pace and distance on screen during outdoor runs, rides, hikes and more and see a workout intensity map in the app that shows your heart rate changes along your route
  • With Active Zone Minutes, feel a buzz when you reach your target heart rate zones during exercise, and celebrate when you earn extra minutes outside of exercise
  • Get a 90-day free trial of the Fitbit Premium to help you stay active, sleep well and manage stress. Unlock it all in the Fitbit app. (Valid payment method required. Cancel before free trial ends to avoid subscription fees. Offer valid for new Premium users only).Operating temperature: -20° to 60° C
  • Use 24/7 heart rate to track resting heart rate & better measure calorie burn. Syncing to mobile devices requires Bluetooth LE and internet connection. Syncs with Mac OS X 12.2 and up, iPhone 5S and later, iPad 5 gen. and later, Android 7.0 and later
  • See your SpO2 nightly average and range on wrist, and view trends over the past week in the Fitbit app (SpO2 is not available in all markets. The SpO2 feature is not intended to diagnose or treat any medical condition or for any other medical purpose)
  • Track your skin temperature each night to see how it varies from your personal baseline (Not available in all markets. Only available in the Fitbit app and only displays variation. Not intended for medical purposes)
  • Track workouts in real-time with 20+ goal-based exercise modes. It’s also swimproof and water resistant to 50 Meters, so you can track swims, wear in the shower and more
  • Multi-day battery lasts up to 7 days and up to 5 hours when using built-in GPS (varies with use & other factors). Track sleep stages & review your in-app Sleep Score for an easy way to see how well you slept
8
Health Fitness Tracker with 24/7 Heart Rate, Blood Oxygen, Blood Pressure, Sleep Tracker, 5ATM Waterproof Activity Trackers with Step Tracker, Pedometer (S & L Bands Included)

Rating is 4.3 out of 5

Health Fitness Tracker with 24/7 Heart Rate, Blood Oxygen, Blood Pressure, Sleep Tracker, 5ATM Waterproof Activity Trackers with Step Tracker, Pedometer (S & L Bands Included)

  • 【24H Accurate Health Monitoring】Measure your Heart Rate, Blood Oxygen, Blood Pressure and Stress with this Fitness Tracker. Understand your physical state, especially for high-intensity or outdoor work such as high temperature, brainstorming, stay-up and get professional analysis on how to relax in a healthier and better way. Amzhero Fitness Tracker also analyzes sleep quality and score your sleep quality to help you adjust your sleep habits
  • 【24 Sports Modes & Fitness Tracker】Amzhero Fitness Tracker supports 14 sports such as walking, running, mountaineering, swimming, yoga, hiking, cycling, treadmill, etc . Accurately record all-day activities like steps, distance, calories burned, miles walked, active minutes and give professional analysis on improving your sports and daily habit
  • 【Smart Life Partner with You】Check daily workout clearly on a 1.47'' HD bright color display. Create customized fitness schedules and goals, Get vibration alerts for all notifications, including phone calls, texts, and social media app alerts. Never miss a message with smart notifications delivered right to your wrist. You also can check real-time weather and change your music on the smartwatch
  • 【15 Day Battery Life& 5ATM Waterproof】Fully charge for 2 hours, support 15 days standby time. Large capacity and low power consumption design offers longer endurance. Amzhero fitness watch is designed with 5ATM waterproof, you can wear it when washing hands, in the rain and swimming
  • 【1-Year Warranty Promised & Wide Compatibility】Compatible with iPhone, Samsung etc., built-in BLE5.0 and 300mAh lithium-ion battery. Our free APP "Gloryfit" supports iOS 9.0 / Android 6.0 or above smartphones. If you have any questions, please don’t hesitate to contact us with any problem
9
DATAFY Smart Watch for Men Women with Bluetooth Call, Fitness Trackers Watch with Heart Rate Sleep Monitor, Alexa Built-in 1.8" DIY Dial 100 Sports Modes IP68 Waterproof Smartwatch for iOS (Beige)

Rating is 4.2 out of 5

DATAFY Smart Watch for Men Women with Bluetooth Call, Fitness Trackers Watch with Heart Rate Sleep Monitor, Alexa Built-in 1.8" DIY Dial 100 Sports Modes IP68 Waterproof Smartwatch for iOS (Beige)

  • 【24/7 Health Trackers Watch】Fitness tracker watches offer health monitoring features to help you build a healthier lifestyle. Android iOS watch offers 24h continuous real-time heart rate, sleep monitoring (deep/light sleep), blood oxygen (Sp02), stress, guided breathing exercises, menstrual health tracking and sports activity monitoring. 100 exercise modes, monitor steps, distance and calories with real-time statistics at your fingertips.
  • 【Make/Answer Calls & Read Message】Smart watch for android iOS phones with a built-in speaker, when connected to your phone via Bluetooth, you can answer/dial clear calls directly from your smartwatch. You can also read app message notifications (the watch can't send or return SMS, Bluetooth distance 8-10 meters). With smartwatch for women and men, you don't miss any important information when you are working out or can't reach your phone.
  • 【Alexa Built-In & Multifunction】Enjoy the convenience of Alexa on your wrist! The Alexa assistant is built into the smart sports watch. You can control your smart home devices, set reminders, and more from your wrist. Voice feedback is provided through the speaker. Android iOS smart watch for men women comes with useful daily functions, including alarms, timer, music control, weather forecast, drinking reminder, camera control, help us live more convenient, smarter and healthier.
  • 【1.8'' Large Touch HD Screen & DIY Dials】With the latest upgraded technology, this fitness watch for men women equipped with 1.8 inch ultra clear full touch colour screen, smooth and sensitive. The app also provides 100+ exquisite dials, you also can DIY watch background as you like. Running watch suitable for a variety of wearing scenarios, change freedom between sports and leisure, show your unique personality. What you will receive: smart watch*1, charger*1.
  • 【Long Battery Life】This men smart watch is powered by a 300mAh battery. With 100% power, it can last up to 7 days of normal use, 30 days of standby, and only takes 2 hours to fully charge. No more charging every day! It can support android and iOS phones(Android6.0 and above IOS 9.0 and above). *Not suitable for PC or tablet. DATAFY provide life time technical support and 12 months warranty, buy it with confidence.


What types of sensors do fitness trackers use to measure calories?

Fitness trackers typically use a combination of sensors to measure calories. Some of the common sensors used include:

  1. Accelerometer: Most fitness trackers include an accelerometer which measures acceleration and movement. It helps in determining the intensity and duration of physical activities such as walking, running, or cycling.
  2. Heart Rate Monitor: Many fitness trackers have built-in heart rate monitors that measure the user's heart rate. By tracking the heart rate during exercise, the device can estimate calorie expenditure more accurately.
  3. GPS: Some advanced fitness trackers include GPS technology that tracks the user's location and movement. It helps in tracking outdoor activities like running or cycling and can provide more accurate data for calorie calculations.
  4. Gyroscope: Gyroscopes can measure rotation and orientation. They contribute to the detection of specific movements and types of exercises such as swimming or weightlifting.
  5. Skin Temperature and Galvanic Skin Response (GSR): These sensors are less common but are occasionally used to estimate calorie expenditure. They measure factors like body temperature and perspiration levels to calculate the intensity of physical activity.


It is important to note that different fitness trackers may use various combinations of these sensors, and their accuracy in measuring calories can vary.


How do fitness trackers differentiate between moderate and vigorous exercise for calorie calculations?

Fitness trackers differentiate between moderate and vigorous exercise for calorie calculations using a combination of factors and algorithms. The exact method may vary depending on the brand and model of the fitness tracker, but generally, the following factors are taken into account:

  1. Heart Rate: Most fitness trackers monitor your heart rate during exercise through sensors on the device or a connected heart rate monitor. By measuring the intensity of your heart rate, they can estimate the level of effort you are putting into the exercise. Higher heart rates generally signify more vigorous activity.
  2. Accelerometer and Gyroscope: Fitness trackers also utilize built-in accelerometers and gyroscopes to measure movement and detect patterns associated with different exercise intensities. They can track changes in speed, intensity, and direction of movement to get an idea of the intensity level.
  3. Personal Information: When setting up a fitness tracker, users typically input their age, weight, height, and gender. These factors are considered when calculating calories burned during exercise. Different intensity levels may have different metabolic rates for individuals of varying characteristics.
  4. Compendium of Physical Activities: Many fitness trackers use databases such as the Compendium of Physical Activities to match an individual's activity with standardized metabolic equivalent (MET) values. MET is a unit that estimates the amount of energy expended during physical activities. Moderate and vigorous activities have different MET values, allowing trackers to differentiate between them.


Based on these factors, fitness trackers can estimate the intensity level of exercise and provide calorie calculations according to the specific metabolic demands of the activity. However, it's important to note that these estimations are not always 100% accurate and can vary depending on the individual and the quality of the tracker.


Do fitness trackers accurately measure calories burned during activities that involve resistance, such as rowing or using resistance bands?

Fitness trackers may not accurately measure calories burned during activities that involve resistance, such as rowing or using resistance bands. Most fitness trackers rely on algorithms and basic measurements like heart rate, steps, and movement patterns to estimate calorie burn. However, they may not take into account factors like muscle engagement, intensity, and individual differences.


During activities involving resistance, the fitness tracker may not accurately perceive the effort put into the exercise due to the lack of specific sensors to measure muscle engagement or resistance level. As a result, the estimated calorie burn could be inaccurate or underestimated.


For more accurate measurements during resistance-based activities, devices like heart rate monitors or specialized fitness trackers designed for specific sports (e.g., rowing, weightlifting) may be more suitable. These devices often provide more accurate data by focusing on specific metrics relevant to the activity, such as power output, muscle fatigue, or workload.

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