Short answer: A sleep score sums up the quality of your night in one number. Trackers build it from how long you slept, how much time you spent in each sleep phase (light, deep and REM), how often you woke up and how regular your sleep is. A high score means restful sleep; a low one tells you something disturbed your night, and the details show what.
What goes into a sleep score
- Total sleep time: most adults need about 7 to 9 hours.
- Sleep phases: light sleep, deep sleep (physical recovery) and REM sleep (memory, mood, learning).
- Continuity: how often and how long you woke up during the night.
- Timing and regularity: going to bed and waking up at similar times.
- Body signals: heart rate and heart rate variability (HRV) during the night, which show how well you actually recovered.
The four sleep phases
| Phase | What happens | Typical share of the night |
|---|---|---|
| Light sleep | Transition phase; heart rate and temperature drop | About half |
| Deep sleep | Physical repair, immune system, growth hormone | Roughly 13–23% |
| REM sleep | Dreams, memory, emotional balance | Roughly 20–25% |
| Awake | Short awakenings, often not remembered | A few percent |
Typical ranges for healthy adults; they vary with age and from person to person.
How to read your score
Do not worry about one bad night: everyone has them. Look at your trend over a week and at what changed on the nights your score dropped. The most useful question is not "what is my score?" but "what lowered it?".
- Little deep sleep? Often late alcohol, a late heavy meal or a warm bedroom.
- Little REM sleep? Often a short night (REM is concentrated in the last hours) or alcohol.
- Many awakenings? Caffeine, stress, noise, light or a late workout.
- High night-time heart rate? Stress, illness, alcohol or a hard training day.
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Ontdek Bionny 4.07 habits that raise your sleep score
- Keep the same bedtime and wake-up time, also at weekends.
- No caffeine after mid-afternoon.
- Keep alcohol for earlier in the evening, or skip it.
- Eat your last big meal two to three hours before bed.
- Keep your bedroom cool, dark and quiet.
- Put your phone away 30 minutes before sleeping.
- Move during the day and get morning daylight.
How Bionny 4.0 tracks your sleep
Bionny 4.0 measures the four phases of your sleep (light, deep, REM and awake), your sleep duration and distribution, and a continuity score, along with your heart rate and HRV during the night. In the morning, your recovery level tells you how well your body actually recovered. Because the band has no screen, weighs 22 g and lasts up to 30 days per charge, you can wear it every night without thinking about it, and the app is free for life, with no subscription. Discover Bionny 4.0.
FAQ
What is a good sleep score?
Each tracker scales its score differently, so compare yourself with your own average. A steady or rising trend is what you want.
How much deep sleep do I need?
For most adults, deep sleep is roughly 13 to 23% of the night, and it tends to decrease with age.
Why is my sleep score low even though I slept 8 hours?
Length is only one part. Frequent awakenings, little deep or REM sleep, or a high night-time heart rate can lower the score.
Can a band without a screen track sleep well?
Yes. A light, screen-free band is often more comfortable at night, and long battery life means fewer missed nights.
This article is for general information and is not medical advice.
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What is HRV, and how to improve it
What is HRV, and how to improve it