Calorie counting accuracy TomTom Runner 2

YorkshireClaireYorkshireClaire Posts: 2 [Apprentice Traveler]
i have a TomTom Runner 2 and the newest fitbit flex.

Run 5 K -> 393 on FitBit and 529 on TomTom is the Calorie count
Cycle ride of 3 and half hours -> FitBit 1,391 vs TomTom 3,690 Calorie count !!

Yes - both have the same details.. Weight, Height and Female.

which is closest to the truth?

Comments

  • tfarabaughtfarabaugh Posts: 15,625 Superusers
    Likely neither. For cycling, it is using MET tables not HR, so you are comparing apples and oranges with a FitBit. MET tables are scientifically tabulated tables of energy expenditure for a specific activity at varying paces. It uses the MET factor along with your personal stats to come up with an energy expenditure number. Depending on where you fall within the average used to compile the tables it may or may not match you exactly. and since it is not looking at HR it has no way of knowing if your level of effort was beyond what is typical at a given pace, which is what the METs are based on. Ultimately, any devices calorie number is just a guess, regardless of method. HR based is only accurate within a relatively small range of HRs at submaximal efforts, while METs based does not take into account elevation change and HR. You just have to pick a method you agree with and stick to it. Since the FitBit is presumably using your HR while the TT is not, that is likely the more accurate number, but that will vary based on the formula FitBit uses. I personally use the average HR data and put it into an Excel spreadsheet with the standard HR formula, this way I am not relying on the watch to calculate calories and will be consistent regardless of device as I am just using the raw HR data. The TomTom in Gym and Freestyle mode (the only ones that use HR) is right on these numbers (more so than my Garmin or Suunto which also uses the same data but applies an algorithm trying to estimate R-R values).

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
  • YorkshireClaireYorkshireClaire Posts: 2 [Apprentice Traveler]
    Interesting.... neither was my conclusion as well. However, the Fitbit has no HR and the TomTom used my external HR monitor.
    I'll just eat the chocolate bar!
  • tfarabaughtfarabaugh Posts: 15,625 Superusers
    In that case the FitBit is probably using METs or some other standard table of energy expenditure so it is just as unreliable as the TT. Go with what feels right or use the HR reading and an online calculator to determine the actual calories.

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question..
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