Fitbit Sleep Score: what it is, how it works and which features may come soon

Fitbit is the best in the business at tracking sleep from the wrist, and it's now even more simple and effective with the addition of Sleep Score.

Those with Fitbit trackers have long been able to access Sleep Stages graphs and breakdowns, but Sleep Score condenses all the information from your night's sleep and spits it out as a round figure.

You'll find Sleep Score on Fitbit Versa 2, Fitbit Charge 4 and Fitbit Inspire HR.

If you're new to the Fitbit app or Sleep Score, though, you might have a few questions. Below, we'll explain what a good score is, how you can improve it and more features that could come soon.

Does your Fitbit have Sleep Score?

Sleep Score is available through any Fitbit with a heart rate monitor, which includes the Charge 4, Versa 2, Versa, Versa Lite and Ionic.

However, if you want the full hit from Fitbit's array of tracked metrics, you'll need to be a Fitbit Premium member, which lets you also gain insights into your Sleeping Heart Rate and Restlessness.

This gives insights into Sleeping Heart Rate and Restlessness, which then both are added to your Fitbit Sleep Score.

What is a good Sleep Score? How is it calculated?

There's been a lot of change to Fitbit's sleep tracking with the introduction of Sleep Score, but it's all still very intuitive - and this is helped by the can't-miss score right in the middle of sleep section.

“Some feedback we got was to simplify it into a single number so people could come have a simple metric,” said Dr Conor Heneghan, lead sleep research scientist at Fitbit.

So, any score above 80 would be considered a 'Good' sleep, something in the 70s would be 'Fair', and anything below that is… not great. Fitbit says that most users get a score between 72 to 83.

How is this Sleep Score number actually worked out, though?

Well, the number is made by combining three other scores. The first is Sleep Duration, which looks at your length of sleep and compares to your average bedtimes and wake-up goals. It also compares your sleep duration against the average score for your age/gender bracket.

Sleep Depth, the second score, is calculated from how much time you spend in deep sleep and REM within your benchmarks.

The third score, referred to as Revitalization during the beta, is a little more interesting. Here, Fitbit is using data for breathing disturbances and comparing your heart rate during sleep to wake hours.

These checks for breathing disturbances currently don't take any information from the Estimated Oxygen Variation graph, which separately harnesses the SpO2 sensor, but there's a possibility we see this factored into Sleep Score figures in the future, as we detail further in the section below.

More features coming soon to Sleep Score?

When we tried out the Sleep Score beta, it also featured something called the Restoration index. It's here where Fitbit indicated it will look for signs of asthma, allergies and even sleep apnea.

Sleep apnea, where breathing stops and starts during sleep, causes blood oxygen levels to fluctuate.

Fitbit is still yet to receive FDA clearance, and so it can't actually say any tracked patterns are indicative of asthma, sleep apnea or other conditions. What it does instead - at least for now - is just report on big fluctuations.

Read this: Everything you need to know about your Fitbit

In the app, under the 'Learn More' section of the Estimated Oxygen Variation graph, this is clarified further.

"Your Fitbit can't measure the blood's exact oxygen saturation level, but it can detect major changes. Seeing big changes is a clue that you may be experiencing breathing disturbances during sleep," Fitbit says.

So, when could we see the current estimate transform into a more accurate metric that can feed into Fitbit Sleep Score?

“We’re continuing our clinical trials to collect the data to support that final application,” said Heneghan back in August, discussing the company's work with the FDA. “We’re still at the early stages of testing.”

You can bet that when the company does receive clearance - something that's potentially being held up by the Google takeover deal - Sleep Score will improve even further.