Resting heart rate inaccuracy between iPhone app and dashboard

[VivienneS]

Basically I've noticed a discrepancy between the resting heart rate shown on my iphone fitbit app and my mac fitbit dashboard.  This isnt just a one off - it seems to feature in the whole of the history. Ie at its peak on 5 Jul the dashboard shows 58 whilst the app shows 57; yesterday my app showed 48 the dashboard shows 49.  The dashboard is showing one up on the iphone reading all the way through it seems.  I wondered why this would be? Both iphone and dashboard are on the same wifi network and set to the same time zones.

[VivienneS]

Ive just checked the whole months history and 11 readings out of the 31 shown in the month are actually correct - the rest so 2/3rds are one up on the dashboard - never less than the app.

[JohnRi · Accepted solution]

It's simply a rounding error.  On the website, if the reading is 59.6 the website will round up.  But the app truncates to just 59. 

Not sure why they choose two different ways.

It's annoying, but you can ignore it.  The website is just more accurate.

[Colinm39 · Accepted solution]

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@VivienneS wrote:

Ive just checked the whole months history and 11 readings out of the 31 shown in the month are actually correct - the rest so 2/3rds are one up on the dashboard - never less than the app.

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@VivienneS Welcome.. This issue has been with us since the HR models were released.  It's a rounding error between the app and the desktops. I have Windows 7 and the same issue.  Because it is always 1 bpm +/-, I just keep an eye on the trend line.. The low activity HR on my Blaze is accurate comparing my Omron BP machine..Apologies for the lengthy post but maybe others will contribute.

There is a similar problem in the weight recording and the "break lines" are at the .25 and .75 kgs in my case and many have reported that as well because the rounding is up and down.

Here is an example of the HR data from the web page and as you can see it gets a pulse every 1-3 seconds with the bpm. I'm not sure what amount of HR data is taken to get the averages but you can see how it can fluctuate.  Here is 5 minutes of data varying from 48-55 bpm and when you realise the graph of daily HR on the Dashboard is at 5 minute intervals you can see where the rounding can creep in.  The average of this 3 minutes is  49.45669291 bpm.  Here is the time graph from the Dashboard as well and you can see the bpm has rounded up by 1 beat on the PC and it shows as 49 on the Android. This proves the rounding problem is on the PC if we assume you round down under 0.5 of a beat.

8:15:02 AM    3    49
8:15:05 AM    1    49
8:15:06 AM    3    50
8:15:09 AM    3    50
8:15:12 AM    3    50
8:15:15 AM    2    50
8:15:17 AM    3    49
8:15:20 AM    1    49
8:15:21 AM    3    49
8:15:24 AM    1    49
8:15:25 AM    3    49
8:15:28 AM    2    49
8:15:30 AM    2    48
8:15:32 AM    1    48
8:15:33 AM    3    49
8:15:36 AM    1    49
8:15:37 AM    3    48
8:15:40 AM    3    48
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8:15:46 AM    3    48
8:15:49 AM    2    48
8:15:51 AM    3    49
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8:17:58 AM    1    47
8:17:59 AM    3    48
8:18:02 AM    2    48
8:18:04 AM    1    49
8:18:05 AM    1    53
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8:18:07 AM    1    55
8:18:08 AM    3    55
8:18:11 AM    3    55
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8:18:17 AM    3    55
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8:18:23 AM    1    55
8:18:24 AM    3    54
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8:18:57 AM    1    52
8:18:58 AM    2    52
8:19:00 AM    3    51
8:19:03 AM    1    51
8:19:04 AM    3    50
8:19:07 AM    3    50
8:19:10 AM    1    50
8:19:11 AM    1    49
8:19:12 AM    1    49
8:19:13 AM    2    49
8:19:15 AM    3    49
8:19:18 AM    3    49
8:19:21 AM    3    49
8:19:24 AM    1    49
8:19:25 AM    3    50
8:19:28 AM    1    50
8:19:29 AM    3    49
8:19:32 AM    3    49
8:19:35 AM    1    49
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8:19:37 AM    3    50
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8:19:48 AM    3    52
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8:19:53 AM    3    52
8:19:56 AM    3    51
8:19:59 AM    3    51
Average              49.45669291

[VivienneS]

Thank Gents; such a simple explanation but one that satisfies my curriosity.