Put in what your ring, watch or app showed last night. You get your own numbers in both minutes and percent, the one figure a health body actually publishes — total sleep for your age — and what the research does and does not say about the rest.
Last night, as your tracker saw it
7 h 10 m — inside the published 7–9 hoursDeep: 1 h 22 m (19.1% of the night) · REM: 1 h 35 m (22.1%).
| Age | Hours a day |
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This page compares your tracker’s numbers with what is published, and nothing more. It is not a sleep study, it does not score your night, and it cannot tell you whether you have a sleep disorder — if you are tired every day, snore heavily or stop breathing in your sleep, that is a conversation with your doctor.
Sources checked 2026-09-22.
Quick answer: no health body publishes a deep-sleep or REM target. The only sleep figure the NIH puts a number on is the total: 7 to 9 hours for adults, 8 to 10 for teenagers, 9 to 12 for children aged 6 to 12. Everything else you read — “you need 1 to 2 hours of deep sleep” — is somebody’s average dressed up as a requirement. This page converts your tracker’s numbers into both minutes and percent, puts your total against the published range for your age, and tells you honestly what the research says about the rest.
How to use it
Type last night’s total sleep the way your app shows it — 7:10, 7h10, 430 minutes — then the deep and REM figures. Switch the toggle if your app gives percentages instead of minutes; the numbers convert rather than change. Leave one blank if your device only reports the other.
Why this page will not grade your night
A sleep laboratory published its own reference data for 206 healthy adults and ended the paper with a warning that is worth more than any chart: sleep parameters have such large standard deviations that specifying reference values is difficult, and “giving patients feedback about deviations from the norm in their sleep profile may give rise to ill-founded concerns and worry.” That is a sleep centre saying that a “your deep sleep is low” message is more likely to cost you sleep than to buy you any.
Does deep sleep really fall with age? Two published answers
The NIH says the amount of slow-wave sleep peaks in early childhood, drops sharply in the teenage years, and “continues to decrease through adulthood, and older people may not have any slow-wave sleep at all.”
The largest modern meta-analysis — 169 studies, 5,273 healthy adults, all scored under current sleep-medicine rules — found something different: the percentages of deep (N3) and REM sleep did not change significantly with age at all. What fell was the total: about 10 minutes less sleep per decade, 2.1% lower sleep efficiency, nearly 10 more minutes awake after falling asleep, and 0.5% more light N1 sleep per decade.
Both are published, and they are not as contradictory as they look: a steady percentage of a shrinking night is still fewer minutes of deep sleep. What neither of them supports is a target you can fail.
What your tracker’s stage numbers are actually worth
Seven consumer sleep trackers were tested against full polysomnography in a laboratory. They were good at telling sleep from wake — epoch-by-epoch sensitivity 0.93 or better — and poor at telling the stages apart: specificity between 0.18 and 0.54, “sleep stage comparisons were mixed”, and, crucially, the devices performed worse on nights with poorer or disrupted sleep. That is precisely the night you go looking at the numbers.
Your device does not measure your brain. It infers stages from movement and heart rate. Even the makers say so: Fitbit’s own help page asks you to watch how things balance out over time and compares you with your own 30-day average, “rather than focusing too much on any one day”.
What the numbers do mean
Three things on this page are solid, and they are the three the tool prints:
- Your total sleep against the published range for your age. That range is official, it comes from the NIH, and it is the number worth acting on.
- Your own minutes and percentages, in both units. Apps show one or the other, which is why people compare a percentage on one device with minutes on another and conclude something alarming.
- Your own trend. One night tells you very little; a fortnight of nights tells you something.
Worked examples
7 h 10 m, deep 82 min, REM 95 min. Inside the published 7–9 hours. Deep is 19.1% of the night and REM 22.1%, with 58.8% light. No official range to pass or fail — and if last week averaged 6 hours, the total is the thing to work on, not the deep-sleep share.
6 h 05 m, deep 35 min. Just under an hour short of the published range. The deep-sleep figure is the one everybody looks at, and the total is the one the NIH actually publishes.
A tracker showing 18% deep at 70 years old. The two datasets above disagree about whether that share should fall with age. Neither says 18% is a problem.
FAQ
How much deep sleep do you need?
How much REM sleep do you need?
Is 40 minutes of deep sleep enough?
Why does my deep sleep change so much night to night?
Do older people get less deep sleep?
Can I compare my Oura numbers with my partner’s Fitbit?
What is light sleep, and why is most of my night light?
My deep and REM add up to more than my total sleep. What went wrong?
More from the site
On the trackers themselves: the Fitbit sleep score, Oura Ring vs Whoop, the best sleep trackers for seniors and how sleep monitoring works.