Calorie accuracy: Fitbit HR vs. Machine (stationary bike) estimate?

[lobrien]

I have a Fitbit HR. When I work out on a stationary bike, the calorie estimate from the HR is consistently lower than the calorie estimate from the machine itself. Which is a more accurate view of my calories, the Fitbit HR (measuring heartbeat, so measuring the truth of *me*) or the machine (measuring mechanics, so measuring the truth of *the work*)? 

[rcofdayton]

I have the same problem, except worse.  I have a heart rate monitor that gives me the calories from the activity.  It knows my age, weight, and average heart rate.  When I enter the same information on a health website, I get a different, and higher, rate.  I take the average of the two.  When I have used fitbit, its calor number is much lower.  Use an average.

[Heybales]

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@lobrien wrote:

I have a Fitbit HR. When I work out on a stationary bike, the calorie estimate from the HR is consistently lower than the calorie estimate from the machine itself. Which is a more accurate view of my calories, the Fitbit HR (measuring heartbeat, so measuring the truth of *me*) or the machine (measuring mechanics, so measuring the truth of *the work*)? 

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The machines with watts that know your body weight really could be the most accurate - because behind treadmills, they are the most used test equipment in labs where measured calorie burn is done in studies - so the formula's are really good.

In fact, average rider is about 22% efficient in producing energy on a bike, so of the average watts produced by the body, it's only 22% of the watts to the bike, and of course watts converts to calories (1 watt hour = 0.8598452 kcal)

Now, does the machine use those nice formula's, or something simple like above?

If you can get the readings from it after next workout and compare. So just like pace and incline would need to be the same throughout the workout to use such a formula, for bike resistance and cadence need to be the same.

http://www.exrx.net/Calculators/CycleMechMETs.html

Once you decide if the machine is close or not for a workout, you can just use it's values.

Because yes, it could have the potential of being more accurate than HRM. The formula is.