Distance accuracy

[GaryD15]

Hi all. I am really sorry if this has come up before.

I do a reasonable amount of running, I track with both MapMyRun and the Fitbit Blaze. For the longest time, the Blaze always ended with a lower mileage than mapmyrun, not by a huge amount but around 5% less than mapmyrun.

That was fine, but suddenly now it has gone the other direction. I did 7 miles last week and the Blaze showed 8 miles. Ran 16 (according to Mapmyrun) and Fitbit showed it as 17.8 miles. Any idea what could have caused this? I use the connected GPS for the Blaze on a Galaxy S9 which is the same device for mapmyrun. I did have stride length set to auto but would it suddenly change that?  I already tried lowering the stride length to a (a guess, for sure) lower amount but I hesitate to go much lower with it since 25.7 already seems to be very small. 

Thank you all for your time!

Moderator edit: Subject for clarity 

[GaryD15]

Update: nothing from Fitbit. Seems like it's a common issue with the blaze since and update recently 

[RicardoFitbit]

Hi @GaryD15, welcome to the Community Forums! Sorry for the delay in responding your post.

I appreciate the information and details that were shared in your post, thanks for troubleshooting this prior to posting too. Let me share with you that Fitbit devices calculate distance by multiplying your walking steps by your walking stride length and multiplying your running steps by your running stride length. We estimate your stride lengths using your height and sex. If your Fitbit device uses GPS and you track 1 or more runs using on-board or connected GPS, we evaluate that data to automatically update your running stride length. For best results, run at a comfortable pace for at least 10 minutes.

If you haven't already done so and prefer to measure your walking/running stride lengths yourself and enter them manually, please check: How do I measure and adjust my stride length?

Note that when you're tracking an activity with GPS, Fitbit calculates your distance using GPS data rather than steps. If you begin moving before you get a GPS signal, the tracker will calculate distance using steps and stride length as described above until a GPS signal is found. Also, please restart your Fitbit Blaze to refresh its performance. 

Let me know if you have any additional questions. 

[GaryD15]

Thank you @RicardoFitbit for your response. I appreciate it, I am having trouble understanding why it suddenly began tracking this way? It was always recording a lower mileage than mapmyrun but suddenly tracks more than mapmyrun. Just last night it tracked 9.27 miles when I ran an 8 mile route? That's even with lowering my stride length from the automatic length it had come up with.  I will try to do those steps again you mentioned and see. But is there anything else that could be causing it? Or any sort of rollback on the blaze firmware I can do?