FitBit Flex: My Initial Thoughts After One Week of Use

I got a new FitBit Flex last Friday, one week ago. It was a replacement for the FitBit Ultra that I’d used for more than a year, before losing it back in March. The Flex is FitBit’s newest activity monitoring product. You wear it as a wrist band instead of clipping it onto your clothing and it has some nice new features that make it, in my mind, an almost ideal tool for the job.

FitBit Flex

The basics

The FitBit Flex tracks nearly every activity captured by the Ultra and One devices. It tracks your steps, distance, activity level, calories, and sleep. The only thing it lacks that the Ultra had was an altimeter that allowed the device to track the stairs you climbed. The FitBit Flex doesn’t do this, but its other features more than make up for that.


I love the fact that you can wear the Flex on your wrist. It is unobtrusive, easy to put on, and then you can forget about it. You don’t have to take it off if you don’t want to. It is waterproof and safe to wear in the shower. I wore it once in the shower just to see, but I’ve taken it off since because it felt weird to have it on in the shower. But it is nice knowing you don’t have to worry about it getting wet.

The fact that you wear it on your wrist means you don’t have to remember to clip it on in the morning, or if you’ve left it clipped to your pants in the evening (with the subsequent concern that it might go through the laundry). You can’t really forget it if you are wearing it. And because you wear it on your wrist, you can sleep with it on to easily track your sleeping. With the Ultra I had to put on an awkward wristband and then slip the FitBit Ultra into the wristband. With the Flex, you just wear it to sleep the same way you wear it throughout your day.


The FitBit Flex does not have a display readout like the Ultra did. If you tap the wristband, you’ll see five dots light up for a second. After a second, the dots will steady to indicate how far toward your step goal you are. Each dot represents 20% of your goal. If you see 4 dots, you are 80% to your goal, if you see 5 dots, you’ve reached your goal for the day. And when you reach your goal, the device will buzz gently on your wrist to let you know.

The Flex also has a silent alarm. You can set a one-time alarm, or a repeating alarm, and you can have more than one alarm. This is a wonderful feature. I’ve setup my device to wake me at 6:15 am Monday through Wednesday, and 6:30 am Thursday and Friday. It wakes you with a gentle buzz that is completely silent, save for those vibrations.

It might seem like a downside not to be able to see your steps directly on the device, but the Flex has lower power WiFi via BlueTooth 4 that will sync with your iPhone (and other devices) so that if you want to see your numbers for the day, you simply pull out your phone and open the app.

Capturing sleep data

It is much easier to capture sleep data from the Flex than it was the Ultra for the simple fact that you are wearing the Flex all the time. All you need to do is tell the Flex when you are going to sleep and when you wake up. You do this by tapping the device 5 times. The device gives you a signal that it is now in “sleep tracking” mode. When you wake up, you tap it five times again to turn off sleep mode. Here is what my sleep stats looked like for last night:

Flex Sleep Numbers

Other details

The Flex comes with 2 wristbands out of the box, a large and small. You can buy additional wristbands. It also comes with a wireless USB dongle to plug into your computer that allows the device to sync with your computer. Finally, it comes with a small USB charger dongle that also plugs into your computer. The instructions say that the Flex can go 5-7 days on a full charge. This will vary based on how you use the device. The battery does not last quite as long if you have silent alarms set (the buzzing takes power).

That said, I fully charged my Flex on Monday, May 6 at noon, and as of this writing (Friday, May 10 at 7:50 am) it has about a 50% charge left and that includes the silent alarm every day for the last four days. Given this, I guess I’ll easily make it to Monday at noon before it needs another charge, meaning I’ve gone a full 7 days without a charge.

Activity statistics

I was pleased to see that the switch to the Flex did not mess up the automated scripting I’ve done to pull my FitBit data into a set of Google Spreadsheets. About the only thing that changed was the order that some of the data is presented in the JSON format that is returned from the API call. (If you don’t understand that last sentence, don’t worry about it.).

Otherwise, the Flex captures all of the same activity statistics as the Ultra and One, except for floors climbed, which, as I said, I don’t really miss.


I love the Flex. It makes the ability to capture activity data virtually transparent, in two ways. First, you don’t have to think about it or remember to do anything. You put the wristband on and forget about it. Second, the wristband itself is unobtrusive and goes with just about anything, whether you are working out or wearing formal clothes. It is priced reasonably at $99. At present, there is only one drawback that I can think of and that is, if you want one, you’ll have to wait.

When I checked the FitBit website store a few minutes ago, the Flex devices were backordered 6-8 weeks. You might check your local Best Buy. When I checked my local store last Friday, they had about 6 Flex devices in stock. On Monday they had none. They are going fast, but with good reason. This is a great device.


  1. I am curious about how you feel about the closed ecosystem that fitbit have. I was doing some research last night and was ready to drop £200 on a fitbit flex and fitbit Aria when I noticed the difficulties I would have exporting MY data from the fitbit systems.

    Ok they will allow you to export daily summaries if you pay them for the privilege (!) but even then, that is not the full minute bu minute that the device has captured.

    I think I will keep looking for a more open solution.

    1. Mark, actually, I have full access to all of that data. FitBit provides an API that gives you access to all of your data. You have to ask to be added to the permissions for the API that gives you the minute-by-minute data, but the folks at FitBit granted that request with no trouble. I have a set of Google App scripts that I’ve written that pull down my minute-by-minute data into a Google Spreadsheet each night. It is from this minute-by-minute data that I was able to put together these statistics for my first year of FitBit data.

      Of course, to use the API, you do need to know how to write code, but FitBit also has a very good set of documentation for how to use their API with the oauth authentication method. It’s pretty easy once you get the hang of it. There are plenty of third-parties that have already written apps for the FitBit.

      1. Jamie,
        Thanks for the excellent review. Would you mind providing some of your Google App scripts or a reference you used to help you develop them?


  2. Ah, cool. Bit annoying that they don’t offer a consumer friendly, direct download option but this could be a good alternative. I will have a look. Thanks for that. M

  3. Very excellent review. Thank you very much! I’ve just ordered mine via so I will have to wait 6-8 weeks, but seems worth the wait!

    1. Sky, I had a friend who ordered one about a week ago or so and it also said 6-8 weeks–however, he just got an email saying his device had shipping, so maybe the wait isn’t so long after all.

  4. I’ve had my flex for a week now and love it! Glad I read your review because I was wondering why it wasn’t tracking floors anymore. I kind of miss that. It was fun to read about the interesting things I climbed. Now I know it’s not broken at least! I think the silent alarm is my new favorite feature! I had a hard time finding a flex. I didn’t want to wait 6-8 weeks because we are starting a fitness challenge at work next week. It took driving to 4 different stores that said they were in stock to finally find one! It was worth the miles and burned gas, even at $4.20/gallon!

  5. Hi just got a flex & it is showing differences on my iphone & laptop (both MAC) ie sleep is several hours different & it shows 7000 step target on iphone & 10000 on laptop.Also it shows floors climbed on the dashboard. Why is that shown if it doesnt work ? I love being able to keep it on. I had a fitbit that clipped on but was easy to forget & also to lose.


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