Fitbit Alta HRFitbit Inspire HR
Tech specs 
SizeDevice Dimensions: 15 mm x 10 mm x 35 mm (W x D x L)
(Sizes depend on type of band)
Device Dimensions: 16.2 mm x 12.6 mm x 37 mm (W x D x L)
Small band: Fits wrists 140 mm - 180 mm in circumference
Large band: Fits wrists 180 mm - 220 mm in circumference
MaterialWristband is made of a flexible, durable elastomer. The tracker is made with surgical-grade stainless steel, and the buckle is made with aluminum.The housing is plastic. The classic band is made of a premium, comfortable silicone similar to that used in many sport watches, and the buckle is made of anodized aluminum.
Battery lifeup to 7 daysup to 5 days. Charge time (0-100%): Two hours.
Water-resistanceSweat, rain and splash proofup to 50 metres (swim-proof) - 5 ATM
Weight15 grams20 grams
Sensor3-axis accelerometer, Vibration motor, optical heart rate sensor3-axis accelerometer, vibration motor, optical heart rate sensor
DisplayB&W OLED touchscreenGreyscale OLED Touchscreen
Screen size1.4-inch, 128 x 36 pixel resolution37 x 16mm
ColorsBlack, Blue/Gray, Coral, FuchsiaBlack, Lilac, White/Black
Other- Saves 7 days of detailed motion data – minute by minute
- Saves daily totals for the last 30 days
Activity tracking 
Calories burnedYesYes
SleepYesYes (light, deep, REM)
Heart rate24/7Yes (Stores heart rate data at 1 second intervals during exercise tracking and at 5 second intervals all other times)
Stress & recovery
Pulse Ox
Respiration rate
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSConnected GPS
Running features
Swimming features
Other Clock, auto sleep detection, silent wake alarm, auto exercise recognition.Vo2Max/Cardio Fitness Level, 15 goal-based exercise modes, as well as breathing exercises.
Non-fitness functions 
Smartphone notificationsYesCall, text and calendar notifications
On-board music storage
Connected pay
Affiliate link*Amazon | FitbitAmazon | Fitbit
Read moreReviewReview
*Disclosure: We are a professional review site that receives a small commission from sales of certain items, but the price is the same for you. See our affiliate disclosure page for more details.
**All tech specs and images on this page come from manufacturers. These may change over time as manufacturers sometimes update their devices. While we cannot guarantee absolute accuracy of information on this page, we promise to review this content regularly and do our best to bring you the most up-to-date information. To be absolutely sure of tech specs of a particular device, we recommend checking the manufacturer’s website.