Fitbit Zip Versa - Why does my weight differ between Fitbit Aria and Aria 2?; Aria 2 has been redesigned to provide more accurate measurements than Aria. For this reason, you may notice different readings between the scales.

Aria and Aria 2 estimate your body fat percentage using body impedance. Because several
different methods can determine body fat percentage and none are 100% accurate, the scale's
body fat reading may not perfectly match other scales or manual methods such as calipers.
Why does my weight differ between Fitbit
Aria and Aria 2?
Aria 2 has been redesigned to provide more accurate measurements than Aria. For this reason,
you may notice different readings between the scales.