Mix your own soundscape and drift off.
Steady background sound masks sudden noises like traffic, neighbours or a snoring partner. Tap a sound to play it, layer as many as you like and set a timer to fade everything out after you fall asleep. Everything is generated live in your browser, so there's nothing to download and no ads.
Tip: keep the volume low. Around the level of a quiet shower is plenty, and a timer helps your brain get used to silence later in the night.
Wake up between cycles, not in the middle of one.
Sleep comes in cycles of roughly 90 minutes. Waking at the end of a cycle, rather than from deep sleep, usually feels far less groggy. The calculator adds about 15 minutes for the time it typically takes to fall asleep.
Try going to bed at:
Cycle length varies from person to person (roughly 80–120 minutes). Treat these times as a starting point, not a prescription.
What actually happens while you sleep
A typical night contains four to six cycles. Early cycles are rich in deep sleep; later ones bring longer stretches of REM, when most vivid dreaming happens.
N1 · Drifting off
A few minutes of light sleep. Muscles relax, and the sudden "falling" twitch known as a hypnic jerk often shows up here.
N2 · Light sleep
About half the night. Heart rate and body temperature drop, and the brain produces bursts of activity called sleep spindles.
N3 · Deep sleep
Slow, rolling brain waves. The body repairs tissue, releases growth hormone and is hardest to wake.
REM · Dreaming
The brain is nearly as active as when awake, the eyes dart around, and most of the body is temporarily paralysed so you don't act out your dreams.
Facts you'll want to tell someone tomorrow
Sleep is one of the few things every animal with a nervous system seems to do, and science is still uncovering why.
of your life
Sleeping 8 hours a night adds up to roughly 25 years over an average lifetime.
Longest documented stretch awake
In 1963–64, US student Randy Gardner stayed awake for about 11 days. Sleep researchers now strongly advise against attempting it.
a brain at a time
Dolphins and many birds sleep with one brain hemisphere at a time, keeping the other half alert to breathe or watch for danger.
Wild elephants
Tracked wild African elephants slept only about two hours a day, mostly standing up, and sometimes skipped sleep entirely for nights at a time.
Little brown bats
Among the sleepiest mammals studied, they can spend around 20 hours a day asleep.
Dreams per night
Most people dream several times every night but forget the vast majority within minutes of waking.
The brain's night shift
During sleep, the brain's "glymphatic" system flushes out metabolic waste far more actively than during waking hours.
What adults need
The recommended amount for most adults. Teenagers need more, and no amount of practice trains you to need less.
Why do we write sleep as "zzz"?
The buzzing "z" sound resembles snoring and the steady rhythm of deep breathing. Early 20th-century comic strips popularised "zzz" in speech balloons above sleeping characters, and the convention spread around the world with comics, cartoons and, later, the internet. Today it's practically a universal emoji in letter form. Many languages also have their own sounds for sleep:
Simple habits backed by sleep science
- Keep a steady scheduleGoing to bed and waking at the same time every day, weekends included, is one of the most powerful ways to anchor your body clock.
- Get morning daylightBright light soon after waking tells your internal clock it's daytime, which makes it easier to feel sleepy in the evening.
- Keep the bedroom cool and darkMost people sleep best in a slightly cool room, around 16–19 °C (60–67 °F), with as little light as possible.
- Mind the caffeine clockCaffeine has a half-life of around five hours, so an afternoon coffee can still be in your system at bedtime.
- Dim screens and lights before bedWinding down in low light for the last hour gives melatonin a chance to rise naturally.
- Don't fight insomnia in bedIf you can't sleep after about 20 minutes, get up, do something calm in dim light and return when you feel sleepy.
This page is for general information only and is not medical advice. If you regularly struggle with sleep, loud snoring or daytime sleepiness, talk to a doctor.
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