How is sleep score calculated?

[Clive18]

Hi

I am somewhat confused as to how the time asleep score is calculated. 

I have one night where the reading is 6hr 54min asleep and 1hr 6min awake.. This gave a score of 39/50

Today I have a reading of 6hr 52min asleep and 59min awake. This gave a time asleep score of 29/50.

This is a significant difference for what appears to be a very similar set of stats. 

Could you provide a better explanation for this 

Thxs

Moderator edit: Updated subject for clarity

[SilviaFitbit]

Welcome to the Community @Clive18. Thanks for the details mentioned, I'll be happy to clarify your question about sleep score. 

Your overall sleep score is a sum of your individual scores in sleep duration, sleep quality, and restoration, for a total score of up to 100. Most Fitbit users get a score between 72 and 83. Sleep score ranges are:

• Excellent: 90-100
• Good: 80-89
• Fair: 60-79
• Poor: Less than 60

Your restoration score provides insight into how restful your sleep was. The score is based on your sleeping and resting heart rates and how much time you spent tossing and turning. You receive a higher restoration score when your sleeping heart rate is lower than your daytime resting heart rate. 

You can improve your sleep score by working on your overall sleep habits, heart health, and activity levels: 

• Exercise earlier in the day or at least 3 to 4 hours before you go to sleep (source).
• Maintain a consistent sleep schedule (source). For more information, see What should I know about setting a sleep schedule?
• Meet the CDC’s recommended 150 active minutes per week (source). 

I'll be around if you need further assistance. 

[Clive18]

Hi

Thanks for your answer but it did not answer my question.. I was specifically asking about the Time Asleep score which is a single component of the overall Sleep Score

[LZeeW]

@Clive18   When I get differences the the one you are describing, I look at the "pattern" of the awake time on the graphs.  One day when I had a low score for a decent Time Asleep, I had a big chunk of time laying in bed before falling asleep -- how long it takes to fall asleep is known as sleep latency.  Sleep latency is one of the things that is looked at in the evaluation of sleep disorders.  Also, if you have one or two bigger blocks of time awake, it might score differently than several short times throughout the night.  The sad answer is that these details are "proprietary", but you might get more insight about you own score by looking at the graphs more closely.

[ElliotZ]

How is sleep score calculated?  Specifically, what is the equation used for calculating sleep score?

[SilviaFitbit]

@ElliotZ A warm welcome to the Community. Thanks for getting in touch about this. 

Your overall nightly sleep score is based on your heart rate, the time you spend awake or restless, and your sleep stages. Your overall sleep score is a sum of your individual scores in sleep duration, sleep quality, and restoration, for a total score of up to 100. Most people get a score between 72 and 83.Learn more about it by checking this article. 

I'll be around if you have any additional questions. 

[ElliotZ]

I'll try to be more explicit in my question.  I would like to see the
equation used to calculate sleep score. I know it includes, minutes
asleep, minutes in REM sleep, minutes in deep sleep, resting and
sleeping heart rate, etc.  The posts already on the Fitbit website tell
me all of that.  What's missing is the EQUATION which ties everything
together and calculates the sleep score. If you can't give the equation
out, please tell me.  Thank you.

--
Moderator Edit: Personal info removed

[RandomAxe]

I'd like to offer an opinion, based only on my observations as an engineer.

I think the algorithm Fitbit uses is more complicated than just a simple equation. I've studies my scores and tried to get a correlation between time in stages and sleep score without good success. It appears that the sleeping heart rate profile plays a significant roll in the score. 

As an example, I had 2 nights with near the same total time and time in each stage, but the scores were 63 and 90. Huge difference.  The only significant difference I saw between the to nights was between the HR profiles. The 90 was classic good sleep pattern, gradually downward, leveling out fand then back up.  The 63 night went down more slowly and was still trending down when I woke. 

To me this indicates something more complicated and probably a proprietary algorithm. 

Just my opinion. 

[ElliotZ]

Many thanks for your answer.   You clearly understood my question and
answered it appropriately.

--
Moderator Edit: Personal info removed

[Mons_mons]

hello:  

I would like to pose that setting a sleep goal has something to do with the sleep score calculation.   I have the following specifics relating to 2 different days:

                  DAY1      Day2

Awake       1:22           :57       

REM          1:56         1:51

Light          4:40         4:57

Deep         1.08           :45    

RHR          98%           96%  Below resting heart rate

Total Sleep 7:44          7:33

Score         87             90  

Seems to me that Day 1 is better sleep than Day 2.  Why is sleep score higher on Day 2?  The only difference, because I wanted to see what would happen, was that my sleep goals were relaxed from 8:30 (Day1) to 7:15 (Day2) minutes

[Yaya1234567]

So there may be some sort of spreadkey for the optimal HR-levels?

But we really get nothing from fitbit here?

Doesn't seem worth paying for if it's bull**ahem** science... Ayurvedics don't treat Corona just like fitbit doesn't really give insights?

Is the data that is extractable insightful or is it only a copy of the stats in the graphs + hr rate over time?

Just give me a spreadsheet and some real data allready

[ElliotZ]

"Give away the secret  of our proprietary algorithm? Never."  If the
Fitbit is collecting potentially useful data, a clever marketer would
make the case for DIYers to take the data and do their own analyses,
maybe with some helpful apps from Fitbit for a small fee.  OTOH, if the
data collected are only marginally useful, I'm not sure what a good
strategy would be for Fitbit or for users.  I can't see any quick
resolution because Fitbit doesn't seem to have any motivation to give
away any more information than they already have, i.e., not much.

--
Moderator Edit: Personal info removed

[DenkoB]

I've been searching around the web and in the Fitbit forums for an example of how the sleep score might be calculated based on the data collected.

All I see from Fitbit is high level explanations of what the algorithm takes into account, nothing about the actual calculation. Instead of numbers, we're getting word salad.

As a result, I can't really evaluate the sleep score and don't have much trust in it. As someone else in this thread said, just give me a spreadsheet and some data. Is this too much to ask? It seems so.

If you can shed some light on the actual calculation, I think many of the purchasers of your product would be grateful. Thank you.

[Zardoz99]

Hi Mons_mons a question for you.

I see from your 04-12-2021 message you added up your REM, Light & Deep sleep and came up with 7:44 total sleep time.  Now if you went into the Fitbit app for that day and looked at the “Time Asleep” value they give you just underneath and to the left of the Sleep Score does it equal your calculated total sleep time of 7:44?? I’m asking because mine never does. My Time Asleep never adds to the addition of the three stages Rem, Light and Deep.   

[Dopovo]

Hello @Zardoz99 , 

it's a bug that many other users are reporting. You can read about it here

[Zardoz99]

Thanks Dopovo. Actually, just a few minutes before I saw this message I saw that the numbers do add up on my PC just not on my iPhone. So yes I guess an iOS app problem.  

[Truelibra]

I have a similar concern.  My sleep goal is 7 hours.  Yet when i sleep even 8 hours and 30 minutes (time asleep) I get a 45 obit of 50.

I think the problem is that “time asleep” is not what is being measured.

The other aspects of the sleep score cover heart rate, and deep sleep etc.

Perhaps you should change the label of “Time Asleep”. 

If a person sleeps in more hours than their goal, how can it not be 50 points for TIME ASLEEP ?????????????????????

If I choose to read in bed for an hour before I fall asleep, then sleep 8 hours or more, why would that hour of reading be counted against my TIME ASLEEP?????????