Tracker Showdown: Fitbit One Verse Flex

Fitbit as a company is one of the biggest names in fitness tracking, and their products have pretty much become synonymous with the word fitness tracker. And although they only have a handful of different devices, there are many differences between them and that can make choosing one a little difficult.

So I decided to do a showdown of 2 of their most popular products. Without further ado, here is my Fitbit Flex Vs One showdown.


The One and the Flex share very similar feature sets. They both have an active minutes counter and will track your steps and calories. You also get a silent alarm and sleep tracking. The Flex has the added benefit of automatic sleep detection, which is not a deal breaker since the sleep tracking on the Fitbits isn't very detailed anyway.

An added benefit of the One is that it contains an embedded altimeter, which is a nice bonus if you do a lot of climbing activities. 

TheFitbit one contains an LED interface that has a clock, which is absent from the Fitbit Flex. The display will give you constant feedback depending on your activity. The feedback is however a little basic (mostly numbers) and you only get things like steps, distance, and floors climbed.

However I feel that the less is more approach works very well here considering the units size.

The Flex has a much more simplistic design. You only get a row of five LED lights that are supposed to show you your current progress. So if you are 60% done with your workout than only 3 LEDs will be lit etc

The Fitbit One has a whooping 14 day battery life versus the Flex's 6 to 7 day life. And both devices are water resistant but not waterproof.

Aesthetics And Functionality

The Flex comes in two sizes smaller large and is made of a soft pliable rubber. The actual brains of the unit are very small and are located in the bottom center of the band, which is easily removable. The Flex comes in many different colors (around seven) and there are a lot of customization options available for.

Being a  wrist based tracker, the Flex is a little on the small side. It is around a half an inch wide and a quarter pound in weight.

The Fitbit One is more of a pocket tracker that you can wear pretty much on any part of your body. I found that the device functions best when worn on the pocket as advertised. The One measures about a inch in diameter and weighs about the same as the Flex without the wristband.


Since the feature set is so similar on these two devices, the difference is mainly going to be in the form of accuracy. There are many arguments as to where you should wear a fitness tracker but the general market seems to be leaning towards wrist based devices. The only problem with wrist based fitness trackers is that they tend to read non related actions like arm movement or typing as part of your step metrics.

Pocket warm trackers on the other hand are less likely to record unrelated activity but they may suffer from an accuracy problem at lower intensity levels.

I was curious to see if there would be much of a difference in recorded metrics if I placed my tracker on the wrist or on my pocket. I tested both the Fitbit Flex and the One over a period of a week to see how their tracking performed. 

The step counters were about identical and their was maybe a 3% margin of error. I did not go out of my way to see if I can make the step counters change depending on my activity. I tested running, cycling, and the stair master machine at the gym for each of my one hour workouts.

At the end of the day, these two Fitbits are very similar and I find it hard to recommend one over the other. It really comes down to where you prefer to wear your tracker and if you need the ability to count floors climbed or not.

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Alex Fischer