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Fitbit Sense 2

FitbitSmartwatch

Sense 2

Released 29 September 2022.5Press releaseblog.google/products-and-platforms/devices/fitbit/fitbit-sense-2-versa-4Read 23 October 2026Blog post dated Sep 29, 2022: Sense 2 is now available at $299.95 (USD) at Fitbit.com, Google Store and select global retailers. The date uses the stated availability. Last checked 23 October 2026.

Case size
Not available
Platform
Proprietary
Display type
OLED
Battery life
144h

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General

Series
Sense4Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Fitbit names the product Sense 2 in its Sense line and calls it its most advanced health-focused smartwatch.
Model numbers
FB521, FB521BKGB-US, FB521SRWT-US, FB521GLBM-US1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Regulatory notices name Model FB521 with FCC ID XRAFB521. The retail colour model numbers come from the Abt listings.19Retailer pageabt.com/Fitbit-Sense-2-Graphite-Aluminum-Shadow-Grey-Strap-Advanced-Health-Fitness-Smartwatch-24mm-FB521BKGBUS/p/182315.htmlRead 23 October 2026Abt lists manufacturer model FB521BKGB-US. FB521SRWT-US and FB521GLBM-US are on the sister Abt listings. FB521 is the model in the manual.
GTIN / EAN
810073611429, 810073611443, 81007361143619Retailer pageabt.com/Fitbit-Sense-2-Graphite-Aluminum-Shadow-Grey-Strap-Advanced-Health-Fitness-Smartwatch-24mm-FB521BKGBUS/p/182315.htmlRead 23 October 2026Abt lists FB521BKGB-US with UPC 810073611429 (Graphite Aluminum with Shadow Grey band).
Announced
24 August 20224Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Blog post dated Aug 24, 2022. Pre-orders started that day with worldwide availability that fall.
Status
Available2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026The Google Store sells Sense 2 at 249.95 USD on the access date. That is a current price, not the launch price.
Predecessor
Not available
Successor
Not available
Launch price (US)
$299.954Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Versa 4 is available for $229.95 and Sense 2 is available for $299.95 (USD). US prices exclude sales tax.
Launch price (EU)
€299.9514Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026UVP 299,95 EUR, marketed from September 2022.15Press articlepcwelt.de/article/1206707/fitbit-sense-2-vorgestellt-hier-finden-sie-alle-infos.htmlRead 23 October 2026PC-Welt (Germany) at the launch: Die Fitbit Sense 2 kostet 299,95 Euro. German prices include VAT. Tech Advisor states EUR 299.95, GBP 269.99 and USD 299.95.
Markets
US, GB, DE, AU2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026US, GB, DE and AU Google Stores offer the model with a Buy button. Current prices are not launch prices.
Colours
Shadow Grey / Graphite Aluminum, Lunar White / Platinum Aluminum, Blue Mist / Soft Gold Aluminum2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Colors: Shadow Grey / Graphite Aluminum, Lunar White / Platinum Aluminum, Blue Mist / Soft Gold Aluminum.
Segment
Smartwatch2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Page title: Fitbit Sense 2 Smartwatch. The Aug 24, 2022 Fitbit blog calls it a health-focused smartwatch.
OS updates promised
Not available
Security updates until
Not available

Case

Front and side, drawn to scale.

Case size
Not available
Case shape
Rectangular14Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026Gehäuseform: eckig (square).
Case material
Aluminium1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Materials: the housing and buckle on Sense 2 are made of aluminum.14Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026Gehäusematerial: Aluminium.
Case material (as published)
Aluminum1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Materials: the housing is aluminum. The store names the finishes Graphite, Platinum and Soft Gold Aluminum.
Back
Not available
Case dimensions
Height40.5Width40.5Thickness11.2mm(1.6 × 1.6 × 0.4 in)2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Dimensions and weight: length 40.5 mm, width 40.5 mm, height 11.2 mm. The page states no sensor exclusion. The same page states weight 37.64 g without saying whether the band is included, so no weight is stored.
Weight (case only)
Not available
Weight with strap
Not available

Durability

Water resistance
5ATM2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Water resistance: water resistant to 50 m. The Google compare page states 5 ATM.9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026Maker comparison, Water and dust resistance row: Sense 2 5 ATM.
Water resistance standard
IEC 605291Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026IP Rating, printed page 78: Model FB521 has a water resistance rating of IPX8 under IEC 60529, up to a depth of 50 meters. IEC 60529 covers ingress, so no ISO pressure standard is inferred.
Dust and water rating
IP6X, IPX81Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026IP Rating: IPX8 under IEC 60529 up to 50 m, and IP6X dust-tight. Stored as the two published codes.
Dive rating
Not available
Max dive depth
Not available
MIL-STD-810
Not available
MIL-STD-810 tests
Not available
Operating temperature
Min-10Max45°C1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Environmental conditions, printed page 63: operating temperature 14 to 113 F (-10 to 45 C). Non-operating and charging ranges (0 to 35 C) are not stored.

Display

Display type
OLED2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Display: AMOLED display.
Display type (as published)
AMOLED2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Display: AMOLED display.
Screen size
1.58in(4 cm)12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Display size 1.58 inch. Notebookcheck and nextpit state the same. Fitbit publishes no diagonal.14Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026Displaygröße: 1,58 Zoll.
Resolution
336 × 336px12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Display resolution 336 x 336 pixels. Notebookcheck states the same.
Pixel density
Not available
Display area
Not available
Touchscreen
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Navigate Sense 2: color AMOLED touchscreen display and 1 button.
Max refresh rate
60Hz18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Notebookcheck spec box lists 60 Hz. Fitbit publishes no refresh rate. Treated as a stated spec, not a measurement.
Min refresh rate
Not available
Peak brightness
1,000nits12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Display brightness: Up to 1,000 nits. Fitbit publishes no nit figure in the documents read, so this is a spec database claim. Window size and ambient conditions are not stated.
Minimum brightness
Not available
Always-on display
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Adjust always-on display section. The setting reduces battery life.3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Always-on display mode: keeps your display on at all times (may require more frequent charging).
Display cover
Gorilla Glass2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Display: Corning Gorilla Glass 3.
Display cover (as published)
Corning Gorilla Glass 32Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Display: Corning Gorilla Glass 3.

Platform

Platform
Proprietary2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026No OS name is printed on the spec page. The Fitbit blog says the watch is powered by the new Fitbit OS, a proprietary platform with its own Gallery.
OS at launch
Fitbit OS4Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Powered by the new Fitbit OS. No version number is published.
Software
Not available
Latest OS
Fitbit OS, firmware 220.317Maker product pagesupport.google.com/googlehealth/answer/14236725Read 23 October 2026Fitbit firmware release notes: Sense 2 latest listed version 220.31 (bug fixes and improvements) on the access date. No Fitbit OS major version number is published.
Works with
iOS, Android2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Requirements: Apple iOS 16.4 or higher, Android OS 11.0 or higher, current on the access date.
Phone requirement
Google Health app on a compatible device running Apple iOS 16.4 or higher or Android OS 11.0 or higher2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Requirements: the Google Health app on a device running Apple iOS 16.4 or higher or Android OS 11.0 or higher. This is the current requirement. The 2022 launch requirement may have been lower.
App store
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026The Fitbit Gallery offers Fitbit apps and clock faces. Tom's Guide states third-party apps cannot be downloaded.17Reviewtomsguide.com/news/fitbit-sense-2Read 23 October 2026Review: you don't get access to third-party apps. You can download custom watch faces but not third-party apps. The Sense 2 and Versa 4 cannot.
Voice assistants
Amazon Alexa1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Voice Assistant: Amazon Alexa Built-in. Needs the phone app running in the background. Not available in all countries.3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Smarts and more: Alexa Built-in.
Chipset
Ambiq Apollo4 Plus12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Platform: Ambiq Apollo4 Plus, ARM Cortex-M4 at 96-192 MHz. Fitbit publishes no chip and Notebookcheck says it does not disclose the SiP. Ambiq's own presentation says Apollo4 powers the Sense product line, which supports the chip family but not the Plus suffix.16Press articleambiq.com/wp-content/uploads/2022/12/Key-to-the-Future-of-Electronics.pdfRead 23 October 2026Ambiq presentation: Apollo4 powers Inspire, Versa and Sense product lines of Fitbit, and Versa 4, Sense 2 and Inspire 3 were launched in August 2022.
Process
Not available
CPU cores
112Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Same Platform entry: one ARM Cortex-M4 core.
CPU configuration
CountCoreMax clock (GHz)
1Arm Cortex-M40.192
Source12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Same Platform entry: ARM Cortex-M4 at 96-192 MHz. 192 MHz is stored as the maximum.
Max CPU clock
0.192GHz
GPU
Not available
Low-power coprocessor
Not available

Memory

RAM
2.75 MB12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Same entry: 2.75 MB on-chip SRAM, stored as 0.00275 GB with 1000 MB per GB. No maker figure exists.
Storage
4GB18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Performance and runtime: the manufacturer has installed 4 GB of internal storage, usable for apps and watch faces. Fitbit publishes no storage figure. Routes and music cannot be stored.

Health sensors

Heart rate sensor
Multi-path optical heart rate sensor1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: multi-path optical heart rate tracker. The Google Store spells it Multi-path optical heart rate sensor.2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Sensors and components: multi-path optical heart rate sensor.
ECG capability
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: multipurpose electrical sensors compatible with the ECG app and EDA Scan app. The ECG app is not available in all countries.2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Sensors: multipurpose electrical sensors compatible with ECG app and EDA app. ECG not available in all countries.
Blood oxygen sensing
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: red and infrared sensors for oxygen saturation (SpO2) monitoring.
Skin temperature sensing
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: on-wrist skin temperature sensor. Track your skin temperature changes: nightly variation from a personal baseline. Not available in all markets.
Blood pressure feature
None12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Blood pressure: No. The maker sensor list and feature pages have no blood-pressure feature.
Body composition sensor
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026The complete sensor list in Sensors and Components has no bioelectrical impedance sensor.12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Body composition: No.
Skin conductance (EDA)
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: electrical sensor to measure skin conductance (cEDA) for stress detection. Manage stress: continuous EDA identifies body responses.4Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Sense 2 has a new Body Response sensor for continuous electrodermal activity (cEDA).
Medical clearances
ECG app: FDA clearance, ECG app: EU clearance, Irregular Heart Rhythm Notifications: FDA clearance, Irregular Heart Rhythm Notifications: EU clearance3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Heart section: the ECG app assesses heart rhythm for atrial fibrillation. Clearance wording is in the Fitbit blog.5Press releaseblog.google/products-and-platforms/devices/fitbit/fitbit-sense-2-versa-4Read 23 October 2026Footnote and text: the ECG app on Sense 2 and the Irregular Heart Rhythm Notifications on both watches have FDA and EU clearance. Only in select countries, not for people under 22 or with known atrial fibrillation.

Motion and environment sensors

Accelerometer
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: 3-axis accelerometer.2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Sensors and components: 3-axis accelerometer.
Accelerometer range
Not available
Gyroscope
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: gyroscope.
Barometric altimeter
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: altimeter, which tracks altitude changes.
Compass
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026The complete sensor list in Sensors and Components has no compass or magnetometer. Gadgets & Wearables also lists Compass: No.12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Compass: No. Geomagnetic: No.
Ambient light sensor
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: ambient light sensor.
Depth gauge
Not available
Depth gauge range
Not available
Water temperature sensor
Not available

Health and fitness

Health features
Continuous heart rate, Heart rate alerts, Irregular rhythm notifications, ECG app, Blood oxygen app, Heart rate variability, Sleep tracking, Sleep stages, Stress tracking, Readiness score, Cycle tracking1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Today and sleep sections: sleep stages (REM, light, deep) and sleep score, stress management score, readiness score (Premium), menstrual health tile, high and low heart rate notifications after 10 inactive minutes, heart-rate variability under Advanced health metrics, oxygen saturation. Daily readiness score needs Fitbit Premium. Irregular rhythm notifications and the ECG app come from the Fitbit blog.3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Heart rate tracking, high and low heart rate notifications, irregular heart rhythm notifications, ECG app, HRV, breathing rate, SpO2, sleep tracking and sleep stages, Stress Management Score, Daily Readiness Score, menstrual health tracking. The Daily Readiness Score is a Premium feature in the manual.
Fitness features
Automatic workout detection, VO2 max, Pool swim, Interval workouts, Turn-by-turn navigation1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Exercise settings list Pool Length, Interval, Auto Start and Auto-Stop. Track your exercise automatically (SmartTrack, 15 minute minimum). Google Maps gives turn-by-turn directions and needs the paired phone nearby with the app running. View your cardio fitness score (stored as vo2_max, see the Google Health VO2 max help page).3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Fitness features: Cardio Fitness Score estimated from VO2 max, SmartTrack Automatic Exercise Recognition (in app only), Google Maps turn-by-turn directions.11Maker product pagesupport.google.com/googlehealth/answer/14237924Read 23 October 2026Learn about your VO2 max: VO2 max, formerly the cardio fitness score, is estimated during outdoor runs with GPS. The Sense 2 manual names the cardio fitness score.
Sport profiles
Not available
Dive modes
Not available
External sensors
Not available

Safety

Fall detection
No9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026Safety and emergency rows (Safety Check, Emergency Sharing, Medical information, Fall Detection, Emergency SOS, Emergency international calling, Car Crash Detection, Earthquake Alerts): the Sense 2 column is empty for all of them. No fall detection.
Car crash detection
No9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026Same Safety rows: Car Crash Detection is empty in the Sense 2 column.
Emergency SOS
No9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026Same Safety rows: Emergency SOS is empty in the Sense 2 column.
Emergency siren
Not available
Live location sharing
Not available
Dedicated LED flashlight
No9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026No flashlight appears in the Sense 2 sensor and component list. Gadgets & Wearables states Flashlight: No.12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Flashlight: No.

Positioning

Positioning
GPS, GLONASS1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: built-in GPS receiver + GLONASS. Dynamic GPS can use the phone's GPS instead to save battery. No band or dual-frequency claim.4Press releaseblog.google/products-and-platforms/devices/fitbit/versa-4-sense-2Read 23 October 2026Built-in GPS is named for Sense 2.
Dual-band GNSS
Not available
Offline maps
No12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Offline maps: No. The manual requires the phone and background app for Google Maps.

Connectivity

Bluetooth
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Wireless technology: Bluetooth 5.0 radio transceiver and NFC chip.
Bluetooth version
5.01Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Wireless technology, printed page 62: Bluetooth 5.0 radio transceiver and NFC chip.14Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026Bluetooth: 5.
Wi-Fi
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components: WiFi (deactivated, cannot be turned on). Stored as false because the user cannot use it. No Wi-Fi standard is stored.
Wi-Fi standard
Not available
Wi-Fi bands
Not available
Cellular
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026No cellular radio is listed in Wireless technology (Bluetooth and NFC only).
Network
Not available
4G bands
Not available
5G bands
Not available
NFC
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Wireless technology: NFC chip. Contactless Payments section describes the built-in NFC chip.
Contactless payments
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Contactless Payments: set up Google Wallet in the Fitbit app and pay at contactless terminals.3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026Smarts and more: Google Wallet, make purchases from your wrist everywhere Google Pay is accepted.
Payment services
Google Wallet1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Contactless Payments: Google Wallet. The text also names Fitbit Pay for the older service name.
Ultra-wideband
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Wireless technology lists only a Bluetooth radio and an NFC chip. No UWB radio.
Satellite
None9Maker product pagestore.google.com/gb/magazine/google_pixel_watch_compareRead 23 October 2026No satellite feature in any Safety row. Published radios are Bluetooth and NFC. GPS reception is separate.
ANT+
Not available

Audio

Speaker
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Sensors and Components lists Speaker and Microphone. The Google Store rates the speaker at 75 dB SPL at 10 cm. That is not an emergency siren.
Microphones
Not available
Calls on the watch
Phone only1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Answer or reject phone calls and Take on-wrist phone calls: calls go through the paired iPhone or Android phone, which must be nearby with the Fitbit app running. No cellular model exists.
Music on the watch
No12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026On-board music storage: No. Smartphone music control only.

Controls

Buttons
11Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Navigate Sense 2: color AMOLED touchscreen display and 1 button.
Named operating buttons
Button1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Navigate Sense 2: the single button opens the apps menu, returns to the clock face and has long-press and double-press shortcuts.
Crown
None1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Navigate Sense 2 describes only the touchscreen and 1 button. No crown.
Rotating bezel
None1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Navigate Sense 2 describes only the touchscreen and 1 button. No bezel control.
Gestures
Turn your wrist, Briefly cover the watch face with your opposite hand, Triple-tap the screen1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Screen wake setting: Button & motion turns the screen on when you turn your wrist. Turn off the screen: briefly cover the watch face with your opposite hand, except with always-on display. Screen Zoom: Magnify works on a triple-tap.

Battery and charging

Battery capacity
162mAh12Spec databasegadgetsandwearables.com/technical-specs/fitbit-sense-2Read 23 October 2026Battery: rechargeable lithium-polymer battery, 162 mAh.13Retailer pageifixit.com/products/fitbit-sense-2-batteryRead 23 October 2026iFixit replacement battery listing for Sense 2: 0.62 Wh, 3.87 V, 162 mAh. 162 mAh x 3.87 V = 0.627 Wh, which agrees. It is a parts listing, not a teardown. Gadgets & Wearables, Notebookcheck and nextpit also state 162 mAh. Two Argos listings print 260 mAh, which is not used.14Spec databasenextpit.de/smartwatches/google-fitbit-sense-2Read 23 October 2026Batteriekapazität (Netto): 162 mAh.
Claimed battery life
ModeWith solarHours (h)
SmartwatchNo144
Always-onNo72
GPSNo5
Source2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Battery and power: battery life of 6+ days, stored as 144 h as a minimum figure. Up to 5 hours with continuous GPS, stored as the gps row. The always-on display, SpO2 and cEDA sensor need more frequent charging. The Google Health support article states up to 12 hours with continuous GPS for Sense 2, a conflict. The model spec page is used because the Oct 2022 Fitbit.com page printed the same 5 hours.6Maker product pagesupport.google.com/googlehealth/answer/14226518Read 23 October 2026Estimated battery life table: Fitbit Sense 2 6+ days. Footnote: with always-on display, Sense 2 has a battery life of up to 3 days (stored as 72 h always_on). The same footnote says Sense 2 has up to 12 hours with continuous GPS, which conflicts with the 5 hours on the model spec page. The 12 hour figure is not stored.10Maker product pageweb.archive.org/web/20221022073607/https://www.fitbit.com/global/us/products/smartwatches/sense2Read 23 October 2026Archived Fitbit.com Sense 2 page, Oct 22, 2022: battery life of 6+ days and up to 5 hours with continuous GPS. Same wording as the current Google Store.
Smartwatch mode (claimed)
144h
AOD battery life (up to)
72h
GPS mode (claimed)
5h
Solar charging
Not available
Charging method
Magnetic pins1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Charge your watch: hold the cable end near the port on the back until it attaches magnetically. The pins on the cable align with the port on the back.
Charging guidance
Not available
Max charging power (watch)
Not available
Fast charging
Yes5Press releaseblog.google/products-and-platforms/devices/fitbit/fitbit-sense-2-versa-4Read 23 October 2026Fast charging gets a full day's worth of battery in just 12 minutes.
Quick charge claim
Charge time12 minUse time24 h1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Charge your watch: charge Sense 2 for 12 minutes for 24 hours of battery life. The usage workload is not named.
Charge 0 to 80% (claimed)
Not available
Full charge time (claimed)
120min1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Charge your watch: charging fully takes about 1-2 hours. The Google Store spec page states two hours and is stored.2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026Battery and power: the Oct 2022 Fitbit.com spec text states charge time (0-100%): two hours.

Measured

Peak brightness (measured)
Not available
Battery life (measured)
144h18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Battery life: with all measurements active, worn around the clock, automatic training detection on, no extensive workouts and the always-on display off, the Sense 2 lasts exactly six days (144 h). Firmware and brightness are not stated. The always-on display test (just under four days) has no exact figure and is not stored.
Battery tests (measured)
TestHours (h)
Mixed use, always-on display off144
Source18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Same test: always-on display off, all measurements active, automatic training detection, no extensive workouts. 6 days converted to 144 h. With the always-on display on it lasted just under four days, which is not stored as a number.
Full charge time (measured)
95min18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Battery life: 0 to 99 percent after 85 minutes on a 24-watt power supply and another 10 minutes for the last percent. Stored as 95 minutes for 0 to 100 percent. 0 to 80 percent took one hour. Test unit with the supplied charging cable and a 24 W adapter. The maker claims two hours.

Strap

Lug width
24mm3Maker product pagestore.google.com/us/product/fitbit_sense_2Read 23 October 2026The store shows an accessory shop headed Shop 24mm attach accessories. Fitbit publishes no lug width in a spec table, and the connector is proprietary, so this is the maker's attach size only.18Measurementnotebookcheck.net/Fitbit-Sense-2-Smartwatch-review-Automatic-activity-recording.717608.0.htmlRead 23 October 2026Case and features: the strap is 24 millimeters wide and can be changed without tools. It is not a standard clasp, so 24 mm is the strap width, not a lug width for standard straps.
Quick-release strap
Yes1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Change the band: slide the flat latch button toward the band, pull the band away. Attach by pressing until it clicks. No tools.
Strap system
Proprietary latch connector. Fitbit Sense, Versa 3 and Versa 4 bands are compatible.1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Change the band: Fitbit Sense, Fitbit Versa 3, and Fitbit Versa 4 bands are compatible with Sense 2. Band latches on the back. No lug width is stated in the manual.
Strap material
Other1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Materials: the supplied band is a flexible, durable elastomer similar to the material used in many sports watches. Other preserves that wording without guessing silicone, HNBR or fluoroelastomer.
Strap
Classic band2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026What's in the box: Classic band (Small and Large).
Strap sizes
SizeWrist (min) (mm)Wrist (max) (mm)
Small140180
Large180220
Source1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026Band size, printed page 63: Small band fits a wrist of 140 to 180 mm (5.5 to 7.1 in), Large band 180 to 220 mm (7.1 to 8.7 in). The Google Store page prints different ranges (130 to 180 mm and 165 to 220 mm). The manual is preferred. These are the supplied straps.

Regulatory

FCC ID
XRAFB5211Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026USA FCC statement: Model FB521, FCC ID XRAFB521.
SAR limb (US)
Not available
SAR limb (EU)
Not available
Other certifications
RED (2014/53/EU), UK Radio Equipment Regulations 2017, IEC 62368-1:2014, IEC 62368-1:2020 + A11:2020, ISED Canada (IC: 8542A-FB521)1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026EU section: Fitbit LLC declares Model FB521 compliant with Directive 2014/53/EU. UK section: Radio Equipment Regulations 2017. Safety Statement lists IEC 62368-1:2014 and IEC 62368-1:2020 + A11:2020. Canada section lists IC 8542A-FB521. These are model declarations, not medical, military or diving certifications.

In the box

In the box
Fitbit Sense 2, Classic band (small & large), Charging cable1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026What's in the box: watch with small band, charging cable and an additional large band.2Maker product pagestore.google.com/us/product/fitbit_sense_2_specsRead 23 October 2026What's in the box: Fitbit Sense 2 Classic band (Small and Large), charging cable.
Power adapter in box
No1Owner's manualstorage.googleapis.com/support-kms-prod/Cxknk8y9NHEphUUIYGTQvRVIFq1RZyQuGQ0dRead 23 October 2026What's in the box lists the watch, bands and the charging cable. No power adapter. The cable plugs into a USB port or a UL-certified USB wall charger.

Warranty

Manufacturer warranty (source market)
1year8Maker product pagesupport.google.com/product-documentation/answer/14815834Read 23 October 2026Fitbit Limited Warranty: new products carry one year from purchase, two years for EEA residents who bought in the EEA. Devices bought on or after July 11, 2023 fall under the Google Hardware Warranty Center terms. Stored as the US one-year term.

Compare with

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Variants

Each variant lists only what differs from the specs above.

Model numberGTIN / EANMarketsColours
FB521BKGB-US810073611429USShadow Grey / Graphite Aluminum
FB521SRWT-US810073611443USLunar White / Platinum Aluminum
FB521GLBM-US810073611436USBlue Mist / Soft Gold Aluminum

Sources

We read 21 sources for this smartwatch. The numbers match the markers in the sheet.

  1. Read 23 October 2026Backs 51 fields
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