Sleep Calculator — Free Bedtime & Wake Up Calculator
Find the best time to go to bed for your wake-up time, the best time to wake up if you sleep now, or how long you sleep — all from 90-minute sleep cycles. Free, instant, no sign-up.
✦ Free forever • No sign-up • 90-minute sleep cycles • 3 calculators
◆When should I go to bed?
Type the time you must wake up — get the best bedtimes for 3, 4, 5 and 6 sleep cycles back. 7.5 and 9 hours are recommended.
Example:
◆I want to sleep now — when should I wake up?
Type the time you plan to sleep (or press “Use now”) — get the best wake-up times for 4, 5 and 6 cycles forward, allowing about 15 minutes to fall asleep.
Example:
◆How long did I sleep?
Type your bedtime and your wake-up time — see your total sleep in hours and minutes, and how many 90-minute sleep cycles that is.
Example:
How to use the sleep calculator
Three steps: type your wake-up time (or the time you plan to sleep), press Calculate, and pick the bedtime or wake-up time that fits your day. The calculator counts in full 90-minute sleep cycles, so waking up at the end of a cycle feels much easier than waking up in the middle of deep sleep. Read the full step-by-step guide with worked examples →
Why use this sleep calculator?
✓ Wake up refreshed, not groggy
Waking at the end of a 90-minute sleep cycle feels far easier than waking in the middle of deep sleep — even if you slept longer in total. The calculator finds those end-of-cycle times for you.
✓ Three calculators in one
Best bedtime for your wake-up time, best wake-up time if you sleep now, and exactly how long you slept — every version of the sleep question, answered on one page.
✓ Fall-asleep time included
Most people take about 15 minutes to fall asleep. The wake-up calculator adds those 15 minutes before counting your cycles, and the bedtime results tell you to get into bed a little early.
✓ The recommended hours highlighted
7.5 hours (5 cycles) and 9 hours (6 cycles) are marked as recommended, because most adults need 7 to 9 hours of sleep a night — for example, 10:00 PM or 11:30 PM for a 7:00 AM wake-up.
✓ Free forever
No account, no sign-up, no limits, no fees. Calculate as many bedtimes as you like, on any device.
✓ Nothing is stored
Your times never leave your browser. Every calculation happens on your own device — nothing is sent to any server.
Guides — sleep better, wake up easier
◆ How to Calculate the Best Time to Sleep
Count back in 90-minute cycles from your wake-up time, pick 5 or 6 cycles, allow 15 minutes to fall asleep — with worked examples, a sleep-cycle table and five habits that make the maths actually work.
◆ Try the calculators above
All three calculators are free and instant — best bedtime, best wake-up time and sleep duration, each with a worked example you can tap to try.
Calculate your best bedtime, free
Waking up groggy is usually not about how long you slept — it is about when you woke up. Sleep runs in cycles of about 90 minutes, from light sleep through deep sleep to dream sleep, and waking up at the end of a cycle feels far easier than waking up in the middle of one. This free sleep calculator finds the best bedtime for your wake-up time: to wake at 7:00 AM, go to bed at 10:00 PM for 6 cycles (9 hours), 11:30 PM for 5 cycles (7.5 hours), 1:00 AM for 4 cycles (6 hours) or 2:30 AM for 3 cycles (4.5 hours). The 7.5-hour and 9-hour options are the ones most adults should aim for.
The calculator also works the other way round: press "I want to sleep now" and it shows the best wake-up times for 4, 5 and 6 sleep cycles from now, allowing about 15 minutes to fall asleep. A third tool works out exactly how long you sleep between any bedtime and wake-up time — for example, 11:00 PM to 7:00 AM is 8 hours, or about 5.33 sleep cycles. Everything is free and nothing is stored: no sign-up, no install, no account. All three calculators run in your browser — your times are never sent to any server. For step-by-step help with worked examples, read the free guide on how to calculate the best time to sleep.
Read the free guide: How to Calculate the Best Time to Sleep →
Frequently asked questions
How does the sleep calculator work?
Sleep happens in cycles of about 90 minutes. Waking up at the end of a cycle feels much easier than waking up in the middle of one. This calculator counts back from your wake-up time in 90-minute steps, or forward from the time you go to sleep, and shows the best bedtimes and wake-up times. For example, to wake at 7:00 AM, the best bedtimes are 10:00 PM (6 cycles, 9 hours), 11:30 PM (5 cycles, 7.5 hours), 1:00 AM (4 cycles, 6 hours) and 2:30 AM (3 cycles, 4.5 hours).
How many hours of sleep do I need?
Most adults need 7 to 9 hours of sleep a night — that is 5 to 6 full sleep cycles of about 90 minutes each. 7.5 hours (5 cycles) is the sweet spot for most people, and 9 hours (6 cycles) is best when you are tired or catching up. Children and teenagers need more, and older adults sometimes need a little less. The calculator highlights 7.5 and 9 hours as the recommended options.
Why is 90 minutes a sleep cycle?
A sleep cycle is the journey from light sleep through deep sleep to dream (REM) sleep, and it takes about 90 minutes on average. Waking up at the end of a cycle — after 4.5, 6, 7.5 or 9 hours — usually feels much easier than waking up in the middle of deep sleep, even if you slept longer in total. Cycles vary from person to person, so these are estimates, not exact science.
Should I count the time it takes to fall asleep?
Yes. Most people take about 15 minutes to fall asleep, so get into bed about 15 minutes before the bedtime the calculator shows. The wake-up calculator already adds 15 minutes for falling asleep before it counts your cycles forward from now.
What if I wake up in the middle of the night?
A short wake-up in the night is normal — most people wake briefly between cycles without remembering it. If you are awake for more than 20 minutes, get up, do something calm in dim light, and go back to bed when you feel sleepy. The duration calculator can still tell you how long you slept in total, including the time you were awake.
Is this sleep calculator medical advice?
No. Sleep cycles average about 90 minutes and vary from person to person, so every result here is an estimate, not medical advice. If you snore loudly, stop breathing in your sleep, feel tired all day despite sleeping enough, or cannot sleep for weeks, see a doctor — a sleep problem needs real medical help, not a calculator.
Is this sleep calculator really free?
Yes. Sleep Calculator is 100% free. There is no account, no sign-up, no limit and no fee — calculate as many bedtimes as you like, on any device. Your times never leave your browser.
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