Versa 2 - difference in calories Fitbit vs Treadmill

[Drewlwd]

I'm using the Versa 2 smartwatch. Walking on the treadmill, treadmill reads 141 cals burned. Versa 2 Smartwatch says 109. Why the difference and which one should I use. Treadmill or Fitbit.

Moderator edit:  updated subject for clarity

[LZeeW]

@Drewlwd   Your Versa 2 uses a Fitbit proprietary algorithm to estimate your calorie burn using your heart rate and other personal demographics.  You don't say what model treadmill you are using, so It's hard to know how it calculates a calorie burn.  If it doesn't track your heart rate, it might be using a system of MET equivalents, along with your walking/running speed and personal demographics.  These are both estimates.  I suspect the real answer is somewhere in between.  You can't edit the calorie burn in a tracked exercise.  So it will log the Fitbit number.  Mentally, I like to underestimate my calorie burn from exercise.