I think it's just a known fact that fitbits are wildly inaccurate, and if that isn't a known fact, it should be. My charge is so off with the step calculator that I just know it routinely overestimates my activities and calories burned by 30-40%.

Sometimes for kicks I'll wear three heartrate monitors and compare them all at once and they're ALL off. The most accurate one will be the polar heart rate monitor with the strap that goes around your chest.

I'll compare the steps of my fitbit to three other pedometers I have on me, my Garmin forerunner 920xt (that has GPS), my moves app on my iphone, and an old school pedometer that straps on my belt. The charge will be over everything else by 30-40%. I'll get 1000 "steps" on the fitbit from driving my car and 2000 for chopping celery.

Fitbits are good to use as baselines to compare them against themselves (was I more or less active today than yesterday? is my heartrate higher than it was 10 minutes ago?) but the information exists in a vacuum because the data is just NOT ACCURATE.

Anyone who depends on a fitbit for accurate data is willfully kidding themselves.