Sleep Quality and the Sleep tab

What Sleep Quality is#

Sleep Quality ("Kvalita spánku" in Czech) is MyBodyAI's own index of the night that ended this morning. It answers one question: how good was last night's sleep, judged on length, structure and calm? It is separate from Sleep Debt, which adds up many nights (Sleep Debt and the Body Clock).

Two numbers can sit on the Sleep tab, and the card tells you which one you are looking at:

• Sleep Quality, with a small "MyBodyAI" tag. It is the score described on this page. We compute it whenever the night gives us enough to work with.
• Device sleep score ("Spánkové skóre zařízení"). When we cannot work out Sleep Quality for a night, the gauge shows the number your device sent and says so: "This is the sleep score straight from your device. MyBodyAI could not work out its Sleep Quality for this night."
• Sleep score with an "estimate" tag. When the device sent no score at all, the number is a rough estimate from the length of the night (below).

The two scales are never mixed in one chart or one average. A window that holds any of our scores is drawn in Sleep Quality only, so changing device or a missing night never looks like a change in your sleep.

Where you see it#

• Sleep tab, the gauge on top. The big number, a word ("Good", "Balanced" and so on, see the words) and the label "Sleep Quality". Tapping it opens "Score trend and scoring" ("Vývoj a výpočet skóre") with a chart of the score over the last 30 nights.
• Sleep tab, seven nights. The bars at the top are the last seven calendar nights with the score on each. Tap one to show that night.
• Overview. The sleep card shows the night against your need together with Sleep Debt, and its "Detail" link leads to the Sleep tab.
• Body Status. Sleep Quality is one of the six tiles under "What the state stands on" (the tile "Sleep quality") and carries 20% of the dial (Body Status).
• Recovery and Training Readiness. Sleep Quality is 20% of Training Readiness, and Recovery has its own sleep parts (Recovery and readiness).
• The card "Sleep → Body Status". A small chain at the bottom of the Sleep tab: Sleep Quality, Debt, Morning energy, Recovery, then your Body Status.

What goes into the score#

The parts and their weights#

Each part is a 0 to 100 sub-score. The score is the weighted average of the parts that exist for that night. The weights below are shares of the total of whatever is present, so a night with fewer parts is not scored lower for that reason.

"With a device score" means the device sent a score for this night. The columns do not add up to 100%, because no night has every part, and the weights only count relative to each other. We divide by the sum of the weights of the parts that are present. A night with a device score, stages, length, recharge and efficiency, but no falling-asleep time and no stored course, has six parts and a sum of 1.05, and each weight is its share of that.

Which parts a device brings: the device score comes from watches and rings that publish one (Garmin, Withings, Oura and COROS do; Polar and Fitbit do not). Stages and length come from nearly every sleep device. The recharge needs a watch that reports Body Battery. The time to fall asleep is timed only by Withings and Oura. The count of wakes needs a night whose stages come with their times.

Your device's score, shifted by your own usual#

The device's score is the most informative single number about a night, because the maker calibrated it on raw motion and heart data. But the same 72 means different things to different people: a good night for someone who usually reads 64, a poor one for someone who usually reads 84. So we move the score by where it sits against your own last 30 days of that same score.

• We take the mean and the spread (standard deviation) of your device's scores over the last 30 days.
• The shift is how far the night is from your mean in spreads, limited to two spreads either way, and then scaled so that two spreads equal 20 points. At your own mean nothing moves.
• It needs at least 3 scores in the window and a spread above zero. Without them the score stands as the device sent it.

The shift never lifts a short night. The usual describes how the maker grades your nights, not how much sleep you need. If the night plus any credited nap is shorter than your sleep need, the shifted score is capped at the device's own number. Downwards the shift works freely.

Stages#

The stage part scores how the night was built from three views, with age and sex targets for deep sleep (targets):

Shares of deep and REM are taken of sleep (deep, REM and light together), because that is how the age targets are stated. Time awake is taken of the whole stretch (sleep plus awake). The ladders:

• Deep: target plus 5 points or more scores 95. From the target up to that, 75 to 95. From 5 points under the target up to the target, 50 to 75. Under that, the share divided by the level 5 points under the target, times 50.
• REM: 22% or more scores 95. 18% to 22%, 75 to 95. 12% to 18%, 45 to 75. Under 12%, the share divided by 12%, times 45. The REM ladder is the same for every age.
• Awake: 5% or less scores 95. 5% to 10%, 95 down to 70. 10% to 15%, 70 down to 40. Above 15%, 40 minus 200 times the excess over 15%, never under 5.

The three results are combined with the weights above, and the part counts in the score at 20% (25% without a device score). It needs at least one hour of recorded night (sleep plus awake) and some measured stage. A view the device does not report is dropped and the other two are re-weighted, see missing stages.

Length against your need#

The length part divides the hours you slept by your sleep need and scores the ratio. Your need is set from your age and sex and tuned by your own good nights, the details are in Sleep Debt and the Body Clock. Under the app's "need" label under the length on the Sleep tab you see the same number.

• The target band is 90% of the need up to 115% of it, or up to the top of the recommended range for your age when that is higher. The recommended range is 7 to 9 hours for adults under 65, 8 to 10 hours under 18 and 7 to 8 hours from 65. For a need of 7h 30m the band therefore runs to 9 hours, which is 120%.
• Between the points the score is a straight line (a night at 89% of need scores 88).
• The step at 90% is deliberate: a night just under the band is a night short of the target, not almost on it. A night under 85% of the need therefore never reads above 80.
• Past the top of the band a long night is penalized: 95 minus 200 times the excess, never under 60. At a need of 7h 30m, a 10-hour night (133%) scores 68.
• Under 70% of the need, the score falls toward the floor: ratio divided by 0.70, times 40, never under 10.

A nap is not part of the night's length here. It can only matter in one place: it counts when we decide whether the night was short of your need for the cap above.

Overnight recharge#

On devices that report Body Battery we read how many points the battery gained during the night. A recharge of 60 or more scores 90. From 45 to 60, 70 to 90. From 30 to 45, 45 to 70. Under 30, the recharge divided by 30 times 45, never under 10. The result is then shifted by your own 30-day mean of the recharge in the same way as the device score (up to 20 points at two spreads), so a person who always recharges 25 points is not rated "very good" for being consistent about it.

Efficiency#

Efficiency is the share of time in bed that you spent asleep: sleep divided by sleep plus time awake plus the time it took to fall asleep (where a device measures that). It is the one definition used everywhere in the app, so the Sleep tab, the coach lines, Sleep Debt and the other scores agree.

The score ladder: 92% or more scores 90 to 100 (92% is 90, 96% is 95, 100% is 100). From 85% to 92%, 70 to 90. From 75% to 85%, 40 to 70. Under 75%, efficiency divided by 75%, times 40, never under 5.

Two rules keep the number honest:

• No time awake reported, no efficiency. An unknown amount of waking is not zero. A device that does not report awake time gets no efficiency part, instead of a perfect one.
• Too perfect to be believed. Where the device does not time falling asleep, time in bed is shorter than real and efficiency drifts toward 100%. At 97% or more with no timed onset we withhold it, on the tab as well as in the score. Where the onset is timed (Withings and Oura), the number stands however high it is.

On the Sleep tab it is the "Efficiency" figure under the length. The colors follow three bands, under 75% low, from 75% to under 90% usual and 90% or more high, which are also the bands the sleep coach words it by.

Falling asleep#

Only Withings and Oura time how long you took to fall asleep, and the part exists only for them. It is the figure "Falling asleep" on the tab, printed with the note "usually 10 to 20 min".

The bands follow the reference range for adults, 10 to 20 minutes. A very fast start is scored one step under the reference band and not as a failure, because dropping off at once is only a warning sign when the night is also short, and the length part already scores that.

Waking in the night#

Efficiency scores the minutes spent awake. This part scores how often the night broke. We count the stretches of waking that lie between your first and your last stretch of sleep. A stretch shorter than 60 seconds is device noise and counts neither as a wake nor as the start or end of sleep, and the waking at the very start or end of the record (time in bed before sleep, minutes before getting up) is not counted either. The Sleep tab prints the same count as "Awakenings".

The count is compared with your own usual from the same device, because each device has its own idea of how long a stir must last to be a wake, so an absolute ladder would grade the sensor, not the night. The usual is the median of the wake counts of your last 30 nights measured by the same source, and needs at least 5 such nights.

A usual under 2 is treated as 2, so a device that usually reports none or one cannot turn a single wake into a doubling. A night without a stored course of its stages has no such part.

The last three nights#

When the device sends scores, a three-night average of them (weighted: today 100%, the day before 85%, two days back about 72%) adds 15% so that one wild night does not swing the number alone. It uses only nights with a score from the device, counted back from the night the score is for. It can be present even when this night's own device score is missing, because earlier nights still carry one.

Missing parts and thin scores#

• At least two nights. We need at least two nights with a recorded length inside the last 5 days. The newest of them is the night being scored. A single night in the window, or none, means no Sleep Quality yet.
• Few parts are pulled toward 50. With one part the score stands as measured. With two parts it keeps 60% of its distance from 50, with three parts 80%, and with four or more it is not damped. A score of 90 on two parts is shown as 74, on three parts as 82.
• Not enough signal. The score needs at least one of: a device score, a length or stages that is no older than about a day and a half, and at least three days of history. If the newest reading is older, a weekly assessment still stands when the device sent at least three readings in the last 7 days; it is then marked as assessed over the week and carries lower confidence. Otherwise the score is withheld and the Sleep tab falls back to the device's own number (above).

A worked example#

A 40-year-old man, need 7h 30m. Last night 7h 10m asleep: deep 1h 20m, REM 1h 35m, light 4h 15m, and 35 minutes awake. His Garmin gave 78, his 30-day mean of that score is 72 (spread 6), the last three nights read 78, 70 and 74, the night charged the battery by 55 points (his 30-day mean 50, spread 10). No timed falling asleep and no stored course.

• Device score: 78, shifted to 88, then capped at 78 because 7h 10m is under his need.
• Stages: deep is 80 of 430 minutes, 18.6%. His deep target is 15%, so full marks start at 20%, and 18.6% scores 89. REM is 95 of 430, 22.1%, scores 95. Awake is 35 of 465 minutes, 7.5%, scores 82. Combined: 0.40 × 89.4 + 0.35 × 95 + 0.25 × 82.4 = 89.6.
• Last three nights: (78 + 0.85 × 70 + 0.7225 × 74) ÷ 2.5725 = 74.2.
• Length: 7h 10m is 95.6% of 7h 30m, inside the band: 95.
• Recharge: 55 points is 70 + 10 ÷ 15 × 20 = 83.3, shifted by half a spread above his mean (+5): 88.3.
• Efficiency: 430 ÷ 465 = 92.5%: 91.

Weights present: 0.35 + 0.20 + 0.15 + 0.15 + 0.10 + 0.10 = 1.05. The sum is 0.35 × 78 + 0.20 × 89.6 + 0.15 × 74.2 + 0.15 × 95 + 0.10 × 88.3 + 0.10 × 91 = 88.54. Divided by 1.05 that is 84.3, so Sleep Quality is 84, "Very strong". Six parts, so no damping. Without the cap on the device score it would have been 88.

Another night on a device with no score, no recharge and no timed onset, but a stored course: 8 wakes against a usual of 8 (ratio 1.0, part score 80), the same stages (89.6), length (95) and efficiency (91). Weights present: 0.25 + 0.20 + 0.10 + 0.10 = 0.65. Sum: 0.25 × 89.6 + 0.20 × 95 + 0.10 × 91 + 0.10 × 80 = 58.5. Divided by 0.65, that is 90.0: 90.

Sleep stages#

What the stages are and where they come from#

A night is split into four kinds of time. Light sleep is the largest share of a typical night, deep sleep is the slow, restorative sleep, REM sleep is where most dreaming happens, and awake is time spent awake inside the night. Your device estimates them from movement and heart signals, so treat a few minutes of difference between nights with caution.

Sources differ in how much they say:

• Some send the course of the night: each stretch with its start and end time. We draw it as a staircase on the card "Sleep architecture" ("Architektura spánku"), with the label "measured course". You can move over it (or touch it) to read each stretch, for example the clock times, "Deep" and "30 min", and open it fullscreen ("View fullscreen"). Two facts appear only for a measured night: "Awakenings" and "To first deep sleep".
• Others send only the totals per stage. The card then draws a proportional band and says: "For this night we have stage totals only, not their order, so we draw no progression."
• Some devices send no stages at all and only the length. The card then says "No sleep-stage breakdown for the selected period."

On a period view (7, 30 or 90 days) the card shows the average split over the staged nights of the window, not one night.

The stage shares printed on the tab are shares of sleep (deep, REM and light), rounded so they add to exactly 100, and the awake time stands beside them in minutes. The card "Sleep architecture · 14 nights" under the hypnogram shows one bar per night for the last 14 nights, the height being time in bed, and the shares of the night you tap.

Targets by age and sex#

Deep sleep gets shorter with age, and women keep more of it for longer. We score deep sleep against a target for your age and sex, based on published sleep studies (a meta-analysis of 65 studies by Ohayon and colleagues, 2004, and studies of women's deep sleep such as Van Cauter and colleagues, 2000, and the SIESTA study). The values by decade are our own interpolation of those studies, not figures quoted from them. Between the ages shown we draw a straight line; ages under 20 use the 20-year value and ages over 70 the 70-year value.

A 45-year-old woman is on the line between 18% and 15%: 16.5%. A 55-year-old man: between 12% and 9%: 10.5%.

• Your age is worked out from the date of birth in your profile on the day the night belongs to, so it moves up on your birthday. Without a date of birth the target is 15%.
• The table for women is used when your profile says female. Any other entry, or none, uses the table for men.
• Full marks need the target plus 5 points. A 40-year-old man with 15% deep sleep scores 75 on that view, with 20% he scores 95, with 10% he scores 50.

This is a score against a target, not a medical standard. A low deep share on one night is common and says little. A share that stays low for weeks is worth looking at with your usual habits (late alcohol, a warm room, irregular hours), and with a doctor if it comes with daytime trouble.

When a stage is missing#

A stage a device never reports is not a measured zero. Some devices and older exports give no REM figure at all. A night with no REM, with the deep and light figures present, is scored from deep and awake alone: their weights (40% and 25%) are re-scaled to 100%. If deep is the missing one, REM and awake carry the part. A device with no stage columns at all, but with time awake in bed, has no stage part for that night, and the score then rests on the other parts and costs a little confidence rather than reading as "0% deep, 0% REM".

The stage part is dropped for a night when the recorded sleep plus awake is under one hour.

Stages that cannot be right#

Some devices over-report deep sleep. We do not give such a night full marks. The stages of a night are set aside when any one of these is true: deep sleep is over 35% of sleep (deep, REM and light together); deep sleep is present with no light sleep at all; or the stages add up to more than 105% of the night's length. The stage part is then missing from Sleep Quality, the "deep sleep rebound" credit in Sleep Debt is not given, and the Sleep tab prints: "The deep-sleep share is unusually high. Your device likely over-reported it, so treat this breakdown with caution."

What counts as a night#

The night window#

One rule decides which sleep is "the night" and which is a nap, for every device and for the MyBodyAI phone app:

• The night of a date is sleep that reaches into the window from 21:00 to 09:00 on your clock.
• A nap is sleep wholly between 09:00 and 21:00. It is kept separately.
• A date with no sleep in the window keeps its daytime sleep as the night, so a person who works nights is not charged a sleep debt for the sleep they had.

The night is filed under the day you wake up. The label above the gauge reads "Night 3 → 4/11" for the night from the evening of 3 November to the morning of 4 November, followed by the clock times of the night and "this morning" or "yesterday morning". When the night shown is not the last one, the label carries a chip "older data, last recorded night".

How long a night may be#

A sleep length under 30 minutes or over 16 hours is not accepted as the length of a night: the first is a nap or a sensor bounce, the second is not a believable record. Up to 16 hours counts, so a long sleep after a night awake is not thrown away. Sleep Debt counts at most 12 hours of one night. A day's naps are stored up to 12 hours.

Which device's night#

When two connected devices both report the same night, we keep one of them. If the one we keep holds less than 60% of your usual night and another device's staged night of the same date holds at least 75% of it, we take the other, the one nearest your usual night: a short record from one device should not outrank a full night measured by another. Two readings from one device that arrive through two routes are the same night and are never swapped, and a night without stages never replaces one that has them. More on how devices combine is in several devices at once.

An unusual night#

A night that is far off your usual is still counted: you may really have been awake. It earns a notice at the top of the Sleep tab:

• Much shorter: under 60% of your usual night. "The night to 3/11 is much shorter than usual: 2 h 40 min of sleep against your usual 7 h 05 min."
• Much longer: more than 3 hours over your usual. A watch left on at the bedside can file hours of "sleep" that you did not have.

Your usual night here is the middle value (median) of your measured nights over the last 365 days, and needs at least 3 nights of at most 12 hours each.

The notice says "It is counted as it was measured." and offers choices:

• "Use the night from [device] (7 h 20 min)", shown only when another device measured that date;
• "Delete this night": the night is taken out of the day and your scores leave it out; the notice then reads "The night to 3/11 is deleted; your scores leave it out.";
• "Undo", which puts the night back as it was.

The cross closes the notice. It stays closed per night and per state, on every device you use. Deleting a night does not change the data at your device.

A night that arrives late, or not at all#

Nights reach us late as a matter of routine, because a watch writes the night when it next syncs with the phone. Until it arrives:

• Scores for the day are worked out on your usual night (the median of your own last 7 nights) and the day is marked provisional, so a delivery delay does not look like a bad night. It applies only to today and yesterday, only when a whole night is missing, and only for values the device delivered on at least 4 of the last 7 days. When the real night comes in, the day is scored again. Details in Body Status.
• The Sleep tab does not show the stand-in night. It shows your latest recorded night with the chip "older data, last recorded night" and the days since, so you never read an invented night as a measurement.
• When there is evidence of no sleep. If your device recorded the day (steps, stress or heart rate) but no sleep, we classify the night. Only a measured sign that no restorative sleep happened counts as one (the Body Battery recharge under 40% of your usual recharge, with no climb of the battery between the evening and the morning). Then the tab says "Last night's sleep was not recorded" and "No overnight recovery was detected. Below is your last recorded night, not today." With no such evidence the night is flagged but never punished: "Showing your last recorded night below, not today."
• A night that was recorded but short. Under 90% of your need is a short night, under 55% of the need or under 4 hours a very short one. The need used for this is never taken below 6h 40m, so a night under 6 hours is always short. The consequences for Body Status and readiness are in the night rule.

Naps#

A nap is daytime sleep that your device records as its own record, wholly between 09:00 and 21:00. It is not part of the night and does not change Sleep Quality: the length, stages and efficiency of the night stay the night's. What a nap does:

• It appears on the card "Naps" ("Šlofíky"): the total time, how many naps, the average length and a strip of the last days. The card hides itself when the night or period on screen has no nap.
• It counts toward the day's sleep need in Sleep Debt, up to 2 hours a day, and not on a day when the naps are longer than the night (that is a split sleep period, not a nap). See naps in Sleep Debt.
• It can matter for the cap on the device's score: a night that is short of your need only by an amount a credited nap covers is not treated as short.

When two devices record daytime sleep on the same day, the larger figure stands rather than the sum.

When the device sends no score#

If your device sent no sleep score for a night, we still compute Sleep Quality from what was measured, with the weights shifted so that stages and length carry it (the right column of the table). Other parts of the app that read "a sleep score" (the sleep part of Recovery, the quality penalty in Sleep Debt) use a modeled score on our own scale: length against your need with 40%, deep and REM shares with 35% and efficiency with 25%, re-scaled to what the night measured. It is rounded to a whole number and marked "estimate" on the gauge ("An estimate from the length of the night; the device sent no score."). It is never mixed with a device's own scores in one window, and it is never used as the device-score part of Sleep Quality, because it sits on our scale.

The Sleep tab, card by card#

From top to bottom:

1. Header. The tab name, a calendar for past nights and the period switch "Night", "7 days", "30 days", "90 days". A past night is shown with a banner and a way back to today.
2. Notices. The stale-signals notice (which indices are withheld because their signals are old) and the notice about an unusual night (above).
3. The night. The gauge with Sleep Quality, the word and "vs. yest." (the difference against yesterday's night, shown only when yesterday's night exists and the two scores are of the same kind). In the middle the length ("Sleep"), "need ~7h 30m", the difference from your 30-day mean ("+6 % vs your 30-day mean"), the stage bar, and the figures Efficiency, Falling asleep, Time in bed (or "Recorded window" when the device does not time falling asleep) and Breathing disturbances. On the right the seven nights. At the foot three folds: "Score trend and scoring", "Sleep debt" and "Tomorrow's recommendations".
4. The strip "The last 7 days". Up to four tiles: "Sleep length" (mean of the nights, with a bar per day), "Usual night start" (the middle of the start times, with the spread rounded to 5 minutes, needs 3 nights), "Night HRV" and "Resting heart rate" (means over the window; HRV is averaged on a logarithmic scale as in Recovery). Each tile leads to its card.
5. Sleep architecture and Sleep insights ("Spánkové postřehy"). The coach lines carry the measured number and one action, for example efficiency bands (under 75% lower, 90% and up excellent). Its text about deep sleep uses a fixed range of 13 to 20%, not your age target. Premium.
6. Morning energy and Body Clock · 14 days (Morning Energy, Body Clock).
7. Overnight physiology and Sleep architecture · 14 nights. The first shows up to five overnight signals (HRV, resting heart rate, respiration rate, blood oxygen, skin temperature) on one axis for 14, 30 or 90 days, each with your usual range (mean plus and minus one spread, needs 7 nights). A ring marks a night outside the range, and several rings on one night are what separates a bad night from a stress or illness signal. Not a diagnosis. See HRV and the nervous system.
8. Week and weekend and Breathing (shown when the night has blood oxygen, snoring or apnea data).
9. Naps (above).
10. Sleep → Body Status. The chain into your state.

The word and the bars#

The word under the gauge comes from ten bands of ten points: 0 to 10 "Critical", 11 to 20 "Concerning", 21 to 30 "Weak", 31 to 40 "Low", 41 to 50 "Slightly low", 51 to 60 "Balanced", 61 to 70 "OK", 71 to 80 "Good", 81 to 90 "Very strong", 91 to 100 "Elite". In Czech: Kritické, Znepokojivé, Slabé, Snížené, Mírně snížené, Vyvážené, V normě, Dobré, Velmi dobré, Vynikající.

The word waits before it changes: it follows the score only once the score is 3 points beyond the edge of the next band, judged on the last 30 nights before this one. A score parked at 70 and 72 does not flip between "OK" and "Good" every morning. The number, the color and the ring always show the exact value. The Overview speaks a coarser four-word ladder for the same score.

When it updates#

• When the night arrives. The score is set from the night when your device delivers it, and it is scored again if the night changes (for example when a better source's night is chosen or a night is deleted).
• Not during the day. The number does not change with the clock. The page uses a stored result for up to 5 minutes, and a sync or a choice about a night refreshes it sooner.
• Past days are recalculated from the data we hold for that day when you open them, so late data or a changed calculation can make an old day differ a little from what you saw then (how MyBodyAI works).
• Your baselines (the 30-day means used above) move one day at a time with new nights.

Free and Premium#

Since 1 November 2026 the free plan shows today's Body Status and the safety alerts. The Sleep tab, Sleep Quality, its history, the stages and the coach lines are Premium, and so is the 7-day trial that includes them. Your data keeps arriving and nothing is lost. See plans.

Energy pacing mode#

The mode does not change Sleep Quality or the Sleep tab. It changes the words and surfaces that ask for movement (energy pacing).

What you can do#

• Wear the device to bed and let it sync in the morning. Length, stages and the wake count all come from the night.
• Keep the same device for the night. A score never mixes two devices' scales, but the comparison with your own usual needs a stretch of nights from one source.
• Read the seven bars, not one night. One poor night is normal, a week under your usual is worth a look.
• Check the weakest part. A low length points at the bedtime, low efficiency at time awake in bed, many wakes at the room or the evening before.
• Use the unusual-night notice. If a watch filed hours of sleep you did not have, delete the night.

MyBodyAI is a wellness app, not a medical device. Sleep Quality describes signals from your device and does not diagnose a sleep disorder. If you struggle with sleep or tiredness for weeks, or your partner sees pauses in your breathing, see a doctor.

Frequently asked questions#

Why is my Sleep Quality different from my device's sleep score?#

Because it is a different number. Your device's score is one of eight parts, and we shift it by how it compares with your own last 30 days. We then add your length against your need, the stages against targets for your age and sex, efficiency and the wakes. A night that your device rates generously but that was shorter than your need can therefore read lower with us. A tag next to the name says which number you are looking at.

Why is my Sleep Quality low after eight hours of sleep?#

Length is only 15% to 20% of the score. A long night with a lot of time awake (low efficiency), many wakes against your usual, a low deep share for your age or a poor device score still reads lower. Open "Score trend and scoring" and look at the figures under the gauge: efficiency under 85% or a deep share well under your target is usually the reason.

Why does the Sleep tab show my device's number instead of Sleep Quality?#

We could not work out Sleep Quality for that night. Typical reasons: the device sent a score but no length (then we have nothing to build the other parts from), only one night in the last five days, or the newest readings are too old. The tab says "MyBodyAI could not work out its Sleep Quality for this night" and shows the device's number so you are not left with nothing.

Is my deep sleep too low?#

Compare it with the target for your age and sex in the table, not with another person's. A share below target on one night is common. Devices estimate stages from movement and heart signals and the estimates differ from one device to another, so look at weeks, not nights. We do not diagnose anything: if a low share comes with heavy daytime sleepiness, see a doctor.

Why does it say my night was much shorter than usual?#

Because the night was under 60% of your usual (the median of your nights over the last year) or because a watch filed a sleep period too short to be the whole night. If another device of yours measured that date, the notice offers its night. If you really slept little, leave it: the night is counted as measured. If the watch was lying on the table, delete the night and the scores leave it out.

Does a nap raise my Sleep Quality?#

No. A nap is not part of the night. It counts toward the day's sleep need in Sleep Debt, up to 2 hours a day (naps).

Why did my score change after a sync?#

Because the night arrived late. Before it came in, the day was scored on your usual night and marked provisional. When the real night is in, the day is scored again and may move. The same happens after you choose another device's night or delete one.

Why is there no REM or no deep sleep on my night?#

Your device did not report that stage for the night, or it reported stages we set aside as impossible (deep over 35% of sleep). A stage that is not reported is left out of the score, not counted as zero, and the other stages carry the stage part.

Does Sleep Quality diagnose a sleep problem?#

No. It is an estimate of how the night went, built from your device's signals. It cannot tell you why a night was poor and it does not detect sleep disorders. See a doctor if poor sleep lasts for weeks or if you or someone close to you notices pauses in your breathing during sleep.