How does Fitbit Inspire 2 calculate mileage?

[richardoe]

how does fitbit calculate mileage? I get varying mileages with roughly the same number of steps

Moderator Edit: Clarified subject

[LZeeW]

@richardoe   If you aren't using GPS, then your Fitbit uses steps x stride length to calculate distance.  When you use GPS, your Fitbit uses the mapped distance.  I don't use GPS often -- my Versa 3 has built in GPS and it uses a lot of battery.  When I used connected GPS, I got different distances for the same daily walk.  This is due to known GPS measurement error.  When I look at my daily steps and distance (no GPS at all), sometimes the math is off by a little bit.  Most of the time the calculation is correct.

[richardoe · Accepted solution]

I also noticed an anomalous result yesterday. I took my fitbit off before going to bed and it read 10,700 steps for the day. The next morning  it showed 12,300.I didn't do extra steps while sleeping?