How Much Sleep Do You Need?

Consensus ranges from sleep medicine bodies and pediatric guidelines. Children's figures include naps; adults' mean one overnight block.

Two misreadings to avoid. The older-adult row is not permission to sleep five hours — need barely changes after 65; getting it in one piece does. And these are hours asleep, not in bed: most people spend 20–40 minutes of a night awake, so 7.5 hours of sleep means nearly 8 between lights out and alarm.

The chart is a starting point; your body is the evidence. Chronic short sleep is easy to miss because the tiredness stops feeling like tiredness and starts feeling like your personality:

• You need an alarm every day and snooze it more than once.
• You sleep dramatically longer on days off — a two-hour lie-in is debt being repaid.
• You fall asleep within five minutes. Normal is 10–20; instant is deprivation, not talent.
• Afternoon crashes pushed through with caffeine after 3pm.
• Micro-sleeps — a lost second in a meeting, a mile of road you don't remember. Act on this one immediately.
• Irritability and low mood out of proportion to events.
• Foggy recall — re-reading the same paragraph, losing words mid-sentence.
• More colds, stronger cravings for fast carbohydrates.

People reliably underestimate their own impairment — performance keeps declining while the felt sleepiness plateaus. If several of these are familiar, trust the list over your sense of coping.

"Eight hours" is an average, not a rule. Where you sit in the 7–9 range is largely genetic and stable through adulthood. Genuine short sleepers who thrive on about 6 hours exist, as do long sleepers who need 9 or more — both far rarer than the people who claim to be short sleepers.

Some things legitimately push you to the top of the range for a while: hard physical training, illness and recovery, pregnancy (especially the first trimester), adolescence — 8–10 hours needed and a late-running body clock — and any debt from previous short nights.

To find your figure, record two weeks of sleep on a stretch with no alarm — a holiday works. The first nights run long while you pay off debt; the number your body settles on is your baseline. Our sleep calculator then works backwards from your wake time to a bedtime that fits.

Partly. Six hours a night Monday to Friday leaves you roughly ten hours short by Saturday, and a long lie-in genuinely recovers some of it — the body prioritizes the deepest stages first, which is why recovery sleep feels disproportionately good (see sleep cycles and stages). But the debt isn't free: attention and metabolic markers don't fully recover over a weekend, and short weekdays plus long weekends swing your body clock like jetlag — Sunday night gets harder, Monday worse.

Better to shrink the debt at the source: bedtime earlier 15–20 minutes at a time, wake time steady all seven days, and the lie-in shrinks on its own. In bed on time but still can't drop off? Different problem — see how to fall asleep faster.

Finding your number takes two weeks of honest records, and a notebook by the bed does that fine — if you'll write in it. Its failure mode: you skip the night you got in late, exactly the night that mattered, then face arithmetic on scribbled times.

An app handles the boring parts: sleep and wake times with time slept computed, charts that make the weekday–weekend gap visible, a quality rating plus dream and note fields so you can see whether more hours buy better nights, bedtime reminders for those 15-minute shifts, Apple Health sync, and export to PDF, XLSX, CSV or JSON for a doctor — with iCloud sync and no account or email. Sleep Journal is a manual sleep diary, not an automatic stage tracker: you tell it when you slept, and it records what actually happened rather than an accelerometer's guess — then does the averaging for you.

The figures below come from the two consensus statements clinicians actually use: the American Academy of Sleep Medicine's pediatric recommendations, and the AASM and Sleep Research Society's adult statement, alongside the National Sleep Foundation's ranges. Children's totals include naps; adult figures mean one overnight block.

Regularly sleeping less than seven hours as an adult is where the consensus statement stops hedging: it is associated with worse cardiovascular and metabolic health, more accidents, and worse mood and performance. Everything above seven is a range to find yourself in, not a target to hit exactly.

There is no separate recommendation for stages, because you don't control them directly — get the hours and the stages sort themselves out. But it helps to know roughly what a healthy night holds. Across a typical adult night, deep sleep (N3) accounts for about 13–23% of total sleep and REM about 20–25%, with light sleep filling the rest. On eight hours, that's very roughly an hour and a half of deep and an hour and a half to two hours of REM.

The distribution matters more than the percentages. Deep sleep is front-loaded: most of it lands in the first two or three cycles of the night, which is why a night cut short at the end costs you REM, and a night that starts late or is broken early costs you deep sleep. REM does the opposite — the periods lengthen towards morning, so the last hour before your alarm is disproportionately REM-heavy.

Two practical consequences. Cutting an hour off either end of the night doesn't remove a uniform slice; it removes a specific stage. And the deep-sleep percentage falls naturally with age, which is normal rather than a fault to fix. Deep sleep and sleep cycles and stages go into both in detail — including why consumer stage estimates should be read as trends rather than measurements.

The same: 7 to 9 hours. The adult range covers 18 to 64 as one block, and the widespread belief that you need less as you get older is simply not what the evidence shows. A 55-year-old sleeping six hours is under-slept in exactly the way a 25-year-old is.

What does change is the character of the night, and that is what gets mistaken for a smaller requirement:

• Sleep gets lighter. Less time in deep sleep, more brief awakenings, so the same eight hours feel less solid.
• The body clock drifts earlier. Sleepy sooner in the evening, awake sooner in the morning — a shift, not a reduction.
• More gets in the way. Nocturia, joint pain, menopause, medications, and a rising rate of sleep apnea all fragment nights from the forties onward.
• After 65 the recommendation eases slightly, to about 7–8 hours.

So if you sleep worse at 50 than you did at 30, the answer is rarely "you need less now". It's usually that something specific is breaking the night — and that is worth finding, not accepting.

Teenagers need 8–10 hours, and during puberty the body clock shifts later by an hour or two — a genuine biological change, not defiance. A teenager told to sleep at 9pm often cannot, and then has to be awake at 6:30 for a school bus.

That collision is why the American Academy of Pediatrics recommends middle and high schools start no earlier than 8:30am, and why districts that have moved their start times report students sleeping longer, with better attendance and fewer car crashes among teen drivers. Where the timetable can't move, the levers left are protecting a consistent wake time across the weekend, keeping the last hour before bed dark and screen-free, and getting bright light in the morning — see sleep hygiene.