How does it measure the information accurately?

[kschorg]

Just curious how it calculates my calories burned, number of steps, etc?

[smhermione]

The fitbit tracks your steps when you wear it and any non-walking type exercise should be logged as an activity.  Also, it takes your information for your body and calculates a Basal Metabolic Rate.  Basically, the calories you burn while breathing and being alive.  It adds those together to get your total calorie burn.

[gerrymcd · Accepted solution]

 'Calories burned' are just an estimate based on height, weight, activity level etc.  Which is ok, since the absolute numbers are not that relevant anyway.  What is important is recording numbers and determining if these correspond to a weight/fitness increase or decrease.  If its not an increase you now have a good baseline for change.