Here’s a suggestion to help you keep from obsessing about your tracker numbers: they’re mostly bullshit.

I bought a Fitbit 2 a couple of years ago on the recommendation of someone who saw me doing my 5k run with just a stopwatch (the horror!) If I had a Fitbit, they said, it would tell me both the time and the distance and all kinds of other cool stuff — like my heart rate and my sleep patterns.

So I got one. The first thing I noticed was that the distance it reported wasn’t the same as what I calculated using Google Maps. Oh, I have to carry my phone along, I discovered, since the watch doesn’t have a gps. So I got rigged up to carry my phone, whereupon I discovered it also didn’t agree with Google.

The Fitbit itself only counts your steps, so it makes sense that it could be off, but why was it still off with the phone? Studying the maps it generates, I learned that the sampling rate of the gps is too infrequent to account for all your turns, so quite often it will believe you cut a corner you really didn’t and end up low balling your distance accordingly. Sigh.

Next came an annual physical, where the nurse put one of those heart rate gizmos on my finger. “Aha!” I thought, “A chance to see how accurate the Fitbit is in that department!” I watched the Fitbit display as the nurse removed the finger vise and recorded the number. Wrong again! I don’t remember how far off, but it was not a trivial difference.

I noticed this morning when I got up that it said I had already burned 460 calories, despite only having taken about a dozen steps to fix coffee. Yeah, right.

So what does it do accurately and reliably? Maybe it counts my steps right, although I wouldn’t surprised if that was off too. It does keep good time, as long as you’re within bluetooth range of your phone, so there’s that. So much easier to twist your wrist than pick up your phone, right?

If you’re looking for something other than amusement or to show off how cool you are, save yourself the money. Use a stopwatch for your run, and measure the distance on a map.