&gt; Maybe it&#x27;s looking at my heart rate and extrapolating?<p>Yes. At least that&#x27;s what I hope&#x2F;assume mine is doing.<p>&gt; Anyway, I&#x27;d be very much interested in some kind of fitness tracker that can provide better estimates on caloric burn.<p>The 2nd most accurate formula involves weight and heart rate. <a href="http:&#x2F;&#x2F;fitness.stackexchange.com&#x2F;questions&#x2F;12435&#x2F;is-it-possible-to-measure-calorie-burn-from-heart-rate-alone" rel="nofollow">http:&#x2F;&#x2F;fitness.stackexchange.com&#x2F;questions&#x2F;12435&#x2F;is-it-possi...</a><p>Your Charge HR knows both of those, so I would hope it uses them. That&#x27;s the whole reason I bought one in the first place.<p>It looks like measuring VO2max is even more accurate. But that&#x27;s very annoying and invasive to measure as it involves breathing through a tube.