Fitbit One is a clip pedometer and comes with a built-in altimeter. Fitbit Flex is the more popular version that you can wear on your wrist and does not have an altimeter. Read the comparison report for Fitbit Alta and Fitbit Charge 2 here.

Fitbit One and Flex Comparison Chart

ProductFitbit FlexFitbit One
Battery LifeAround 5 daysAround 10 days
Charge TimeTwo hours approx.One hour approx.
DisplayFive LED lightsOLED display
Release DateMay 2013September 2012
ColorsBlack, Slate, Navy, Tangerine, TealBlack, Burgundy
CompatibilityAndroid, iOS, Windows, OS XAndroid, iOS, Windows, OS X
PC SyncUSB DongleUSB Dongle
BluetoothBluetooth 4.0 compatibleBluetooth 4.0 compatible
Mobile SyncAutomaticAutomatic
Water ResistanceWater resistant (Not water proof)Water resistant (Not water proof)
Operating Temperature-4 deg F to 113 deg F-4 deg F to 113 deg F
App CompatibilityFitbit App, MyFitnessPal, MapMyFitnessFitbit App, MyFitnessPal, MapMyFitness
TrackingActivity and basic sleep trackingActivity and basic sleep tracking
Activities trackedSteps, Distance, Calories burnedSteps, Distance, Calories burned
Alarm and RemindersYesYes
Elevation / StairsNoYes

Fitbit One overview

Fitbit One is a small fitness tracker that is supposed to be on you at all times. It tracks your number of steps taken, measures your calories burned, tracks the number of floors that you’ve climbed and tracks your sleep. It will help you track everything from the food you eat to how much activity that you get in the day. Using this data you can offset the number of calories that you are consuming so that you can lose weight.

This convenient tracker can create personalized fitness plans for you depending on if you want to lose weight or keep your current weight. According to these plans, it creates a daily goal for you so that you can complete that goal and it will let you know by a flower growing on the display itself. This is very convenient for those who do not have much time to keep track of their workout statistics.

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Fitbit One tracks your sleep movements at night when you place it in the flexible wristband provided. To start sleep tracking press and hold the button on the tracker which starts a timer. That is the sleep timer and it tracks the number of hours you sleep. It also senses your movements which tell you how many times you’ve possibly woken up or tossed and turned at night. Fitbit One does not have a heart rate monitor. Check out and compare a list of fitness trackers with a heart rate sensor here.

The battery inside Fitbit One lasts a little more than one week on a single charge. Synching this device with the Fitbit app is very smooth and once all the data is uploaded to the app, you open a door to a lot of features such as leaderboards and badges. If you have friends added to the website, you can compete with them on a weekly basis.

Fitbit Flex overview

The Fitbit Flex is an activity tracker placed inside a flexible and durable rubber band. The strap is adjustable so you’ll likely find a position suited to your wrist. The tracker can easily be removed from the strap. Since Fitbit sells a variety of different colored bands, you can easily change the color depending on what you like without having to buy a whole new device. Once you wear the tracker, you can check your improvement all day long whether your objective is number of steps, distance travelled, calories used or active minutes, by gently tapping on the device.

Your advancement is shown on the device using the five flashing LED lights giving you an idea of how you are doing without having to use your Fitbit app. The LED lights also show you the remaining charge on the battery. It syncs with your iPhone or Android phone wirelessly using Bluetooth 4.0. As for the battery life you get about five days of use before you have to charge it up. To charge it you take out the tracker out of the band and put it into the charging cable which then plugs into a USB jack.

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Sleep tracking is similar to Fitbit One. You can turn on sleep tracking from the app or tapping on the tracker several times quickly. It gives you a nice graphical display in the app of when you were in deep sleep or restless or awake. You can set an alarm and it will buzz when it’s time to wake up.

Similarities between Fitbit One and Fitbit Flex

  • They are splash resistant but not suitable for swimming.
  • Both have a built-in pedometer.
  • Both have sleep tracking functions with a silent vibration alarm. Fitbit One comes with a breathable wristband in which you can place the tracker to track your movements while you sleep.
  • Both have access to Fitbit dashboard to log your calorie intake and workouts.
  • Both synchronize via Bluetooth to your PC using a dongle / receiver or directly to your iPhone, Android or Windows app.
  • USB charger is included in the package.
  • Activity and sleep reports are provided in both devices with the help of Fitbit app.
  • Both devices are compatible with MyFitnessPal.

Differences between Fitbit One and Fitbit Flex

  • The battery life of Fitbit One is almost double that of Fitbit Flex. In addition Fitbit One charges faster than Flex.
  • Fitbit Flex lacks an altimeter while Fitbit One has a built-in altimeter to measure elevation or stairs / floors climbed.
  • Fitbit One has an OLED (Organic Light Emitting Diode) display which shows your activity status in the form of a flower bar (grows and shrinks depending on your activity levels), steps taken, distance covered, calories burned, stairs climbed and current time. Flex on the other hand has a series of five LED lights which show your daily progress. You need to use the Fitbit app to get more information out of Fitbit Flex.
  • Fitbit One is available only in two colors – Black and Burgundy. However Fitbit Flex has more color choices – Tangerine, Black, Navy, Teal and Slate.
  • Fitbit One is usually clipped to your torso or can be placed in your pocket while Flex is worn on your wrist. The advantage of a wristband is that you are less likely to lose something which is tied to your wrist.
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Compare Activity wristbands

Tips, features and usage for Fitbit One

  • The package you receive will contain the Fitbit One device, a silicone metal clip, USB charging cable, USB receiver for your computer and a Velcro wristband to wear the device while sleeping.
  • You can wear it on your clothing, place it in your pocket, attach it to your undergarments or clip it to your pants.
  • Sleep tracking is based on the amount of movement while you are asleep. Therefore if you are lying still, it will assume that you are sleeping. So you will be disappointed if you are looking for an in-depth sleep analysis which includes detection of different sleep cycles.
  • There are no monthly charges to use the Fitbit website or app. Simply create a free account and start analyzing your fitness data.
  • The pedometer is pretty accurate and will not record random movements like driving or shaking as steps.
  • To track movement while cycling, working out on a stationary bike or elliptical you can clip it below your knee or insert it in your sock to improve tracking accuracy. However it is not built to track non step activities.
  • Fitbit One is primarily built to track step activities like jogging, running, walking or when on a treadmill. It will not accurately track activities like swimming, cycling, yoga, aerobics, weight lifting, etc. You have an option to add non step activities manually in the application or website.
  • Activating the sleep mode requires pressing and holding the tracker’s button for about five seconds.
  • There is no GPS or heart rate sensor in this device.
  • Do not immerse this device in water. It is only resistant to sweat, rain or short splashes of water.
  • This device does not alert you if you have been inactive for a long time. The app will send you short cheerful messages when your goal is near completion.

Tips, features and usage for Fitbit Flex

  • Tracks all step activities similar to Fitbit One. It cannot track other non step activities like biking, weight lifting, or swimming. Steps on the treadmill will be tracked by this device.
  • The Fitbit Flex package includes two adjustable wrist straps of different sizes, the tracker, a USB dongle to sync with your computer and a charging cord.
  • Sleep tracking is based on your arm movements. If you forget to activate the sleep mode, you may manually log in the sleeping hours in the application or website. You need to tap the area below the LED lights repeatedly till it vibrates to activate the sleep mode.
  • This device should not be submerged under water.
  • It cannot display the current time.
  • It does not track your heart rate and does not have built in GPS.