Fitbit Sense

Fitbit Sense

The Fitbit Sense is a full featured smartwatch released in September 2020. Fitbit is one of the first wearble companies and has been producing products for the last 13 years. They are well known for their fitness bands and smartwatches. Google purchased Fitbit in 2019 and the deal closed in January 2021.

Fitbit launched both the Versa 3 and the flagship Fitbit Sense at the same time. These 2 watches have a lot in common. They look nearly identical and have essentially the same hardware inside but the Sense comes with 4 extra health features:

  • Electrocardiogram (ECG) tracking
  • Stress tracking with electrodermal activity sensor (EDA)
  • Dedicated skin temperature tracking (more granular than the Versa 3)
  • High and Low heart rate alerts

The following table shows the differences between the Sense, Versa 3 and Versa 2.

Fitbit Sense Comparison

Unfortunately Fitbit does not disclose the chipset used for the Versa 3. In the past they have used Toshiba processors with Arm Cortex M4 CPUs. We suspect they are using a Toshiba Cortex processor but we are not sure which one but the processor is labeled the Fitbit FBT18SW. Given that the watch is choppy / not smooth when scrolling, we believe the processor used is a underpowered.

Fitbit Sense FBT18SW Processor
Fitbit Sense FBT18SW Processor

This watch is using Fitbit OS, the proprietary operating system for Fitbit smartwatches. While there are some available apps, the number is minimal and you do not have access a vast app store such as the Google Play Store. This is a significant disadvantage and is common drawback for any smartwatch using a proprietary operating system.


The Fitbit Sense has a square watch face design with a aluminum case.  The square design is unique and not all people are fans but that is based on personal preference. The watch is available in gray and gold. This smartwatch is medium sized at 40.5 x 40.5 x 12.4 mm and weighs 44g. The 12.4 mm thickness is not the thinnest and could uncomfortable for some to wear while sleeping.

The Sense comes with a 20mm silicone interchangeable strap. It can also be purchased with a polyester strap. Strap is good quality and comfortable to wear.

You can interact with the watch using the touchscreen or the capacitive button on the side. The touch sensitive side button is one of the worst items on this watch and generates a lot of complaints from owners. It is glitchy, not always responsive and overall a poor substitute for a real button.

The Sense has a 5ATM water resistance rating which allows for swimming and showers. It performs well in pools and showers. The watch comes with a water lock mode that disables the touchscreen.


The screen of the Fitbit Sense is quite good. The 1.58″ AMOLED Touchscreen, with 336 x 336 pixels delivers a high-quality visual experience. Indoors the display is excellent while outdoors it performs well.

While Fitbit claims the screen is using Corning Gorilla Glass 3, the watch can easily get scratched. Both the screen and bezel are susceptible to scratches. This has been a common problem on previous Fitbit watches and the tradition continues with the Sense. We suggest purchasing a screen protector for this watch.

The watch has an always on screen option but this has a significant impact on battery life. The watch allows for custom watchfaces which is a nice feature.


The Fitbit Sense comes with a 246 mAh battery and Fitbit claims that typical usage battery life is 6 days. Real world battery life matches that. If you plan to use the always on display, you will get approximately 2 days of battery life. While battery life is not best in class, it is quite reasonable for a full featured smartwatch.

Connectivity Features

From a connectivity perspective, the Fitbit Sense has good functionality and can receive and respond to notifications from the watch. The watch complements a smartphone well, unlike other smartwatches with limited connectivity functions.

The Fitbit Sense has both a speaker and a microphone and has the ability to answer or place calls via Bluetooth. The microphone can also be used for Alexa or Google Assistant, one of the few smartwatches that offer both voice assistants.

The speaker and microphone work well for both incoming and outgoing calls. The speaker can be used to play music streamed via Deezer, Pandora, or Spotify. Even though the Sense comes with 4GB of internal memory, you cannot store MP3 files on the watch.

The Fitbit Sense does not have a camera and does not have cellular connectivity. On the positive side, it does come with built-in GPS. GPS connectivity is fast and accuracy is fairly good.

Finally, Near Field Communication (NFC) is supported and you can use this smartwatch to make payments using Fitbit Pay. While this is a nice feature it only works with certain banks and cards. While coverage is good in the US, it is not that good in other countries. Check the list of banks on the Fitbit site to confirm your bank is covered if this feature interests you.

Health and Fitness Features

The Sense comes with 8 sensors: Accelerometer, Altimeter, Ambient light, Electrocardiogram (ECG), Gyroscope, Heart Rate Monitor (HRM), Pulse Oximeter (SpO2), Temperature. These cover quite a bit of fitness functions and even some health areas. These sensors allow you to track the following 12 metrics: Blood Oxygen Level, Calories, Distance, Fitness Level, Heart Rate, Menstrual Cycle, Skin Temperature, Sleep, Steps, Stress, Swimming, VO2 Max. Also included are 20+ different sports modes.

As mentioned previously, the Fitbit Sense offers SpO2 monitoring and ECG monitoring which the more affordable Versa 3 does not offer. Since ECG is not available in all countries, check the Fitbit ECG webpage to confirm availability where you live.

While heart rate accuracy at rest is adequate, the Fibit Sense has poor heart rate accuracy for intense training. There are a significant amount of complaints regarding the accuracy from owners. Given the high price tag of this device, the heart rate accuracy is disappointing. If this is an important feature for you, consider another smartwatch.

Fitbit App

The Fitbit Sense uses the Fitbit app, which is very good particularly for fitness and sports tracking. The app is not cluttered, easy to navigate and works quite well. The biggest complaint regarding the app is syncing problems with certain phones.

On the negative side, for the full set of heath reporting, dashboards and insights you need to shell out another $10 per month or $80 per year. This is quite disappointing given the pricepoint of the watch. You can see how the Fitbit app ranks on our Smartwatch Apps Page.

Known Issues

Notification Service Not Running

Numerous owners have received the “Notification service is not running. A phone restart is required to re-enable notifications on your tracker”. Make sure you are using a compatible phone or table. The list is here.

Fitbit also suggests to do the following:

  1. On your phone, open the Settings app > Apps and notifications > Apps.
  2. Tap Fitbit > Battery.
  3. Turn off the Power-intensive prompt option.
  4. Tap Launch.
  5. Turn off the Manage automatically option, and turn on the Auto-launch, Secondary launch, and Run in background options.
  6. Tap OK.

Note that Fitbit is aware of the issue.

Stuck on Fitbit App Download

Numerous owners have indicated that the watch gets stuck on the “To start, download the Fitbit app” screen. You will need to redo all the installation steps again. You may want to try installing the app on a different device. Often times some smartphones do not work well with the Fitbit app and watch.

Fitbit Sense App Issue
Stuck on “To start, download the Fitbit app”

Internal Photos


The Fitbit Sense under-delivers as Fitbit’s flagship. The poor heart rate accuracy is the most common complaint for this watch. Also many people complain about sync issues. Unacceptable at this price point.



Read Review
Watch Type Full Featured Smartwatch
Gender Unisex
Release Date September 2020
Operating System Proprietary - Other
App Fitbit
Supported Devices Android 7.2+, iOS 12.2+
Processor Not Disclosed


Shape Square
Case Size 40.5 x 40.5 x 12.4 mm
Case Material Aluminum
Weight 44g
Strap Width 20 mm
Strap Material Polyester, Silicone
Interchangeable Strap Yes
Watch Colors Gray, Gold
Input Touchscreen, 1 Button
Water Resistance 5 ATM


Screen Size 1.58"
Screen Type AMOLED Touchscreen
Resolution 336 x 336
Pixels per Inch Not disclosed
Always On Yes
Custom Faces Yes
Screen Protection Corning Gorilla Glass 3


Typical Usage Battery Life (Days) 6
Watch Mode Battery Life (Days) Not disclosed
GPS Mode Battery Life (Days) 0.5
Charging System Magnetic
Capacity 264 mAh


Notifications Recieve Notifications and Respond
Bluetooth v5.0
Bluetooth Calling Receive and Place Calls
Bluetooth Music Yes
Speaker Yes
Microphone Yes
Camera No
Cellular No
Near Field Communication (NFC) Yes
Payments Fitbit Pay
WiFi Yes
Voice Command Google Assistant and Alexa
Memory 4GB
Sensors Accelerometer, Altimeter, Ambient Light, Electrocardiogram (ECG), Gyroscope, Heart Rate Monitor (HRM), Pulse Oximeter (SpO2), Temperature
Tracking Blood Oxygen Level, Calories, Distance, Electrocardiogram (ECG), Fitness Level, Heart Rate, Menstrual Cycle, Skin Temperature, Sleep, Steps, Stress, Swimming, VO2 Max
Sport Modes 20+
Warranty 12 Months


Unique Features Google Assistant and Alexa
Advantages Good app
Can respond to notifications and take/place calls
NFC with Fitbit Pay
Disadvantages Heart Rate Accuracy is poor
Limited apps
Monthly fee for premium account
Capacitive button is not great
Verdict The Fitbit Sense under-delivers as Fitbit's flagship. The poor heart rate accuracy is the most common complaint for this watch. Also many people complain about sync issues. Unacceptable at this price point.

Published: January 25, 2021

Fitbit Sense - WatchSmarty
Fitbit Sense

The Fitbit Sense under-delivers as Fitbit's flagship. The poor heart rate accuracy is the most common complaint for this watch. Unacceptable at this price.

Product SKU: Fitbit Sense

Product Brand: Fitbit

Product Currency: USD

Product Price: 430

Price Valid Until: 2021-01-01

Product In-Stock: SoldOut

Editor's Rating: