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What time should you go to bed to wake up rested?

Sleeping in full cycles of about 90 minutes helps you wake up from light sleep instead of the middle of deep sleep. Pick when you want to wake up or fall asleep and this sleep calculator gives you the best times, with your night drawn stage by stage.

01 What do you want to calculate?

Wake-up time

02 Tune it to your body

How long it takes you to fall asleep after lights out. Most people take 10 to 20 minutes.
90 minutes is the average, but it varies from person to person. If you wake up groggy with 90, try 85 or 95 for a week.
Time format

04 Facts worth knowing

What happens while you sleep

Eight science-backed facts that explain why the time your alarm goes off matters as much as how many hours you sleep.

  • Cycles of about 90 minutes

    Every night you go through four to six cycles. They last 90 minutes on average, though they can range from 80 to 110 depending on the person and the night.

  • Four stages per cycle

    N1 is the transition (a few minutes), N2 takes up about half the night, N3 is deep sleep, and REM is when you dream most vividly.

  • Sleep inertia

    If your alarm goes off during deep sleep, you can feel groggy for anywhere from a few minutes to half an hour or more. At the end of a cycle, sleep is lighter.

  • Caffeine lasts longer than you think

    Its half-life is about 5 hours (2 to 10 depending on the person). A coffee at 4 PM still has about half its effect at 9 PM.

  • Light and screens at night

    Bright light, including the blue light from screens, delays melatonin. Dim the lights and screen brightness an hour before bed and get natural light in the morning.

  • Naps of 20 or 90 minutes

    A 10 to 20 minute nap recharges you without leaving you groggy. If you need more, complete a full cycle of about 90 minutes. Avoid naps late in the afternoon.

  • Cool room: 64 to 68 °F (18 to 20 °C)

    To fall asleep, your body temperature drops slightly. A cool, dark, quiet bedroom makes that shift easier.

  • Consistency counts

    Going to bed and getting up at the same time, weekends included, stabilizes your body clock. Staying up late on Saturday feels like a little jet lag.

Sleep hygiene in five habits

  • Use your bed for sleep. If you can't fall asleep within about 20 minutes, get up, do something calm in dim light and come back when you feel sleepy.
  • Eat a light dinner two or three hours before bed and avoid alcohol at night: it helps you nod off, but it fragments sleep in the second half of the night.
  • Move during the day. Regular exercise improves sleep; if it's very intense, try to finish a few hours before bedtime.
  • Build a short routine of 20 to 30 minutes: a warm shower, reading on paper, stretching or slow breathing. Always in the same order.
  • Keep your phone out of bed. Turn on night mode and don't check email or social media right before sleep.
When to see a doctor

If it takes you more than 30 minutes to fall asleep, or you wake up and can't get back to sleep three or more nights a week for months (persistent insomnia). If you snore loudly with pauses in your breathing, wake up gasping or feel very sleepy during the day even after enough sleep (possible sleep apnea). Also if you nod off unintentionally while driving.

This calculator is for information only and is not a substitute for advice from a healthcare professional.

01How it works

Three steps and done

  1. 01

    Choose what you want to know

    If you already have a wake-up time, use “I want to wake up at…”. If you know when you're going to bed, use “I want to fall asleep at…” or the “I'm going to sleep now” button.

  2. 02

    Tune it to your body

    Change how many minutes it takes you to fall asleep and how long your cycles last. Choose your age to see which options fall within the recommended hours.

  3. 03

    Pick a time and save your alarm

    Tap a time to see your night stage by stage, download the alarm for your calendar or copy the summary to share it.

02How it's calculated

Sleep in cycles, not hours

Sleep isn't one even block. During the night your brain goes through cycles of about 90 minutes: it enters light sleep (N1 and N2), drops into deep sleep (N3) and ends in REM sleep, when the most vivid dreams happen. At the end of each cycle sleep is lighter, and it's common to wake for a few seconds without remembering it.

That's why your alarm time matters. If it goes off during deep sleep, you get sleep inertia: that heavy, foggy feeling that can last anywhere from a few minutes to half an hour or more. If it goes off at the end of a cycle, waking up is usually easier, even if you slept a little less.

The calculator does the math for you. For each option it adds or subtracts full cycles (1 to 6) plus the time it takes you to fall asleep, which defaults to 15 minutes. If you want to wake up at 7:00 AM with 90-minute cycles, going to bed at 9:45 PM gives you six cycles (9 hours) and at 11:15 PM gives you five (7 and a half hours).

Five or six cycles, between 7.5 and 9 hours, line up with what the National Sleep Foundation recommends for adults: 7 to 9 hours. Three or four cycles will do for a short night, but not as a habit. Fewer than three leave little real rest.

Cycles aren't exactly 90 minutes for everyone. They range from 80 to 110 depending on the person, their age and the night, and the last ones tend to be longer because of REM. Use the calculator as a starting point: if you wake up groggy for a week, move the cycle length by five minutes and compare how you feel.

  • Bedtime or wake-up time

    Two modes and a sleep-now button. Six options with full cycles, from most to least rest.

  • Quality of each option

    Recommended with five or six cycles, acceptable with three or four, and too little rest with fewer than three.

  • Recommended hours by age

    National Sleep Foundation ranges for children, teens, adults and people 65 and older.

  • Your night in a chart

    Illustrative hypnogram with light, deep and REM sleep, cycle by cycle and with real clock times.

  • Alarm for your calendar

    Download an .ics file with your bedtime and wake-up time, reminder included.

  • Remember and share

    Your settings are saved on this device; copy a summary or a link with your times. 12- or 24-hour format.

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04FAQ

What people ask us

How many hours of sleep do I need?
Adults ages 18 to 64 are advised to get 7 to 9 hours; people over 65, 7 to 8. Teens ages 14 to 17 need 8 to 10, and children ages 6 to 13 need 9 to 11. These are general ranges: if you sleep within them and feel good during the day, you're on the right track.
Why am I tired even though I slept eight hours?
Your alarm may have woken you in the middle of a cycle, during deep sleep, which is why you feel sleep inertia. Sleep quality, alcohol, afternoon caffeine, irregular schedules or a disorder like sleep apnea also play a role. If the tiredness is constant, it's worth seeing a doctor.
Do all sleep cycles really last 90 minutes?
No. Ninety minutes is a useful average, but cycles range from about 80 to 110 minutes and change through the night. That's why the calculator lets you adjust the length: try one value for a week and compare how you wake up.
Which is better, a 20-minute or a 90-minute nap?
A 10 to 20 minute nap refreshes you without entering deep sleep, so you get up without feeling groggy. A nap of about 90 minutes completes a full cycle and can help if you slept poorly, but it takes longer and, if it's late in the day, can cost you sleep at night. Naps of 30 to 60 minutes are the ones that leave you groggiest.
What time should I stop drinking coffee?
Caffeine has a half-life of about 5 hours, though in some people it lasts much longer. As a rule of thumb, avoid coffee, black tea, colas and energy drinks at least 6 hours before bed, or from noon on if you're sensitive.
Does sleeping in on weekends help me catch up?
It helps a little with tiredness, but it doesn't fully repay your sleep debt, and shifting your schedule a lot throws off your body clock. Getting enough sleep on weeknights and keeping a similar wake-up time every day works better.
When should I see a doctor about my sleep?
If insomnia shows up three or more nights a week for months, if you snore loudly with pauses in your breathing or wake up gasping, if you're very sleepy during the day even after enough sleep, or if you nod off while driving. This calculator is for information only and is not a substitute for advice from a healthcare professional.
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