How does Fitbit Sense measure burned calories?

[KCl94]

Hi there!

Does anybody know how the Fitbit Sense (and maybe all other Fitbits out there) measures the calorie count every day? I never really doubted the numbers I see on the app until I got a Samsung Active 2 last week.

I have been testing the two smartwatches and I noticed that the number of calories I burned every is very different between the two watches. Here is an example of a busy weekend at my job:

	Active 2	Fitbit Sense
Saturday	2465 cal	4531 cal
Sunday	2449 cal	3395
Monday	2622 cal	4432
Tuesday	2271 cal	3121

I work at a restaurant so I move a lot. Before I got the Active 2 I thought that the Sense was overcounting, but now that I got the other watch I am even more confused about these numbers, Any ideas of which smartwatch is giving me more accurate data? 

[JohnnyRow]

The Fitbit includes BMR calories.  Does the Samsung?

See How does my Fitbit device calculate calories burned?  

[KCl94]

Did a quick search and yes, they both include BMR calories in the calculation:

How does Samsung Health measure calories burned per activity? 

[MattJ71]

The Fitbit uses a combination of BMR, weight, steps, heart rate, etc.  It combines all these things into an algorithm that estimates the calories burned.  However, I think there are some important elements that are left out should be included.

For example, a 50 year old man, weighing 190 lbs, bodybuilder/athlete with 7% bodyfat, and a RHR of 55 BPM would probably show to burn less calories than a 50 years old man, 190 lbs, sedentary with 25% bodyfat and a RHR of 75 BPM.

I think Fitbit is fairly accurate for the "average" person, but really skews on the extremes, which is ironic since most Fitbit users might be more on the athletic side.

The Fitbit algorithm doesn't take bodyfat into consideration, which is odd, since the Fitbit Aria records this.  I think it should be plugged into the algorithm somehow.

All in all, it's an estimate at best.  I suspect it could easily be off by 500 to 1000 calories, which makes it effectively useless in my opinion.

[KCl94]

---

All in all, it's an estimate at best.  I suspect it could easily be off by 500 to 1000 calories, which makes it effectively useless in my opinion.

---

Yeah, I am afraid it is just estimating from a fixed formula rather than calculating base on my basic data and HR during workouts.

I did about 20 minutes of a Stair Master session yesterday while wearing both watches. It was sad to see that the Fitbit would not be able to pick up the HR once my bpm was over ~140 (tested multiple times, including the awkward mid-arm placement), while the Active 2 never struggled to keep pace with the handheld scanner on the machine. Interestingly enough, at the end of the session, both watches told me I burned exactly112 calories!