AFFIVANCE
Sleep Calculator
Find the bedtime or wake-up time that fits your sleep cycles, then plan naps, check sleep debt, measure sleep efficiency and more.
- Runs in your browser
- No sign-up
- Nothing is sent anywhere
Sleep cycle calculator
Enter when you need to wake up. We will suggest bedtimes that let you finish a full sleep cycle.
Your sleep options
Your suggested times will appear here.
Sleep cycles vary from person to person and throughout the night. This calculator uses approximately 90 minutes as a simple planning estimate.
Quick sleep tools
Nap timing, sleep duration, sleep efficiency and sleep debt. Each tool works on its own.
Nap calculator
Find your wake-up time for a power nap, short nap or custom nap.
Enter a start time and press Calculate.
Naps of about 10 to 30 minutes tend to cause the least grogginess. Late-day naps can make it harder to fall asleep at night.
Sleep duration calculator
Work out how long you are in bed between bedtime and wake-up time. Midnight is handled for you.
Enter your bedtime and wake-up time.
Time in bed is not the same as time asleep. Use the efficiency calculator to compare the two.
Sleep efficiency calculator
Sleep efficiency is the share of your time in bed that you actually spend asleep.
Enter your time in bed and time asleep.
Formula: actual sleep time ÷ time in bed × 100. Sleep efficiency of about 85% or higher is commonly considered good.
Sleep debt calculator
Estimate how much sleep you owe from recent nights of short sleep.
Enter your target and actual sleep.
Estimate only: (target sleep − actual sleep) × number of nights. Recovery is not always one-to-one.
More sleep calculators
Sleep by age, sleep score, caffeine timing, shift work, jet lag and health-related educational tools.
Sleep calculator by age
See the general recommended sleep range for an age group and a bedtime window that fits your wake-up time.
Choose an age group and press Calculate.
General recommendations from widely cited guidance, not a diagnosis. Ranges for infants and young children include naps.
Sleep quality and score calculator
A simple 100-point planning score built from five sleep factors. The breakdown shows exactly how it is calculated.
Fill in the factors and press Calculate.
This is a personal planning score, not a medical diagnosis.
Multiple wake-up times
Enter your bedtime, or choose sleep now, to see wake-up times for two to eight sleep cycles.
Enter a bedtime and press Calculate.
Wake-up times use a simple 90-minute cycle estimate plus your time to fall asleep.
Caffeine sleep calculator
See how many hours pass between your last caffeine and bedtime, and a rough estimate of what may remain.
Enter the caffeine time and bedtime.
Educational estimate using an average 5-hour half-life. Caffeine sensitivity and metabolism differ a lot between people.
Shift work sleep planner
Get two simple sleep schedules around your shift: sleep after work, or sleep before work.
Enter your shift times and press Calculate.
General planning information only. Assumes 30 minutes to wind down after work and 60 minutes to get ready before you leave.
Jet lag planner
Enter the two time zone offsets yourself to get a general sleep-shift plan. No time zone lookup is used.
Choose your time zones and press Calculate.
General guidance only. Daylight saving changes are not detected, so check your offsets. Individual adjustment speed varies.
AHI educational calculator
The apnea-hypopnea index (AHI) is the number of breathing events per hour of sleep. Enter values from a sleep report to see the arithmetic.
Enter your event counts and hours slept.
Educational calculation only. AHI interpretation and diagnosis require appropriate clinical evaluation.
Insomnia severity screening (ISI-style)
A 7-item screening questionnaire for educational use. It is scored from 0 to 28.
Answer all seven questions and press Calculate.
Screening and educational questionnaire only, not a diagnosis. Condensed adaptation of the Insomnia Severity Index (developed by Charles M. Morin) using the standard 0 to 4 scoring and score bands. If you are worried about your sleep, talk to a healthcare professional.
Sleep calculator guide: cycles, bedtimes and how much sleep you need
Straight answers to the most common questions about sleep time, bedtime and wake-up time calculators.
What is a sleep calculator?
A sleep calculator estimates when to go to bed or wake up so that you finish a full sleep cycle before your alarm. Enter one time and it counts forward or backward in 90-minute steps, including the minutes you need to fall asleep.
How does the sleep cycle calculator work?
It assumes one cycle lasts about 90 minutes. Wake-up time equals bedtime plus time to fall asleep plus the number of cycles times 90 minutes. Most adults aim for five or six cycles, which is 7.5 to 9 hours.
Is 90 minutes exact?
No. Real cycles vary between about 80 and 110 minutes and change through the night, so treat every result as a planning estimate and adjust based on how rested you feel.
How do I use this sleep time calculator?
- Choose Bedtime, Wake-up time or Sleep now.
- Enter your time and how long you usually take to fall asleep.
- Pick an age group to compare each option with a recommended range.
- Choose the option that fits your schedule.
How many hours of sleep do you need by age?
These are general recommendations for total sleep in 24 hours, based on widely cited guidance from the American Academy of Sleep Medicine and the National Sleep Foundation. Ranges for infants and young children include naps. They are not a diagnosis.
| Age group | General range | Notes |
|---|---|---|
| 0–3 months | 14–17 hours | Includes naps |
| 4–11 months | 12–16 hours | Includes naps |
| 1–2 years | 11–14 hours | Includes naps |
| 3–5 years | 10–13 hours | Includes naps |
| 6–12 years | 9–12 hours | Nighttime sleep |
| 13–17 years | 8–10 hours | Nighttime sleep |
| 18–64 years | 7–9 hours | Nighttime sleep |
| 65+ years | 7–8 hours | Nighttime sleep |
What time should I go to bed for my wake-up time?
Approximate bedtimes for common wake-up times on a 12-hour clock, assuming 15 minutes to fall asleep and 90-minute cycles. Six cycles is 9 hours of sleep, five is 7.5 hours and four is 6 hours.
| Wake up at | Bed by (6 cycles) | Bed by (5 cycles) | Bed by (4 cycles) |
|---|---|---|---|
| 5:00 AM | 7:45 PM | 9:15 PM | 10:45 PM |
| 5:30 AM | 8:15 PM | 9:45 PM | 11:15 PM |
| 6:00 AM | 8:45 PM | 10:15 PM | 11:45 PM |
| 6:30 AM | 9:15 PM | 10:45 PM | 12:15 AM |
| 7:00 AM | 9:45 PM | 11:15 PM | 12:45 AM |
| 7:30 AM | 10:15 PM | 11:45 PM | 1:15 AM |
| 8:00 AM | 10:45 PM | 12:15 AM | 1:45 AM |
How each calculation works
- Sleep cycles: wake-up time = bedtime + time to fall asleep + cycles × 90 minutes.
- Duration: wake-up time − bedtime, adding 24 hours when the span crosses midnight.
- Efficiency: actual sleep ÷ time in bed × 100.
- Sleep debt: (target − actual sleep) × number of nights.
- Caffeine: amount remaining ≈ dose × 0.5 ^ (hours ÷ 5).
- AHI: (apneas + hypopneas) ÷ hours slept.
Private by design
Every calculation runs in your browser. Nothing you enter is sent to AFFIVANCE, this website or any third-party service. The only thing saved on your device is your light or dark theme choice.
Sleep calculator FAQ
Short answers to common questions about sleep cycles, bedtimes and wake-up times.
Most adults need about 7 to 9 hours of sleep per night, and many older adults do well with 7 to 8 hours. Children and teenagers need more: roughly 9 to 12 hours for ages 6 to 12 and 8 to 10 hours for ages 13 to 17. Individual needs vary, so treat these ranges as general guidance rather than a diagnosis.
A sleep calculator gives a planning estimate, not a measurement of your sleep. It assumes a fixed cycle length of about 90 minutes and a fixed time to fall asleep, while real sleep varies between people and from night to night. Use the suggested times as a starting point and adjust based on how rested you feel.
A sleep cycle in adults is commonly quoted as about 90 minutes, with a typical range of roughly 80 to 110 minutes. Each cycle moves through lighter sleep, deeper sleep and REM sleep, and the mix changes through the night.
No. Ninety minutes is a simple average used for planning. Cycles can be shorter or longer, and they change over the night, with more deep sleep early on and more REM sleep later. That is why this calculator shows several options instead of one exact time.
Six hours is below the 7 to 9 hours generally recommended for adults. Some people feel fine on less for a while, but regularly getting less sleep than you need can build up as sleep debt. If you often feel tired, aim for five cycles, which is about 7.5 hours.
Not necessarily. Seven and a half hours equals five 90-minute cycles, which is why it appears so often in sleep calculators, but both 7.5 and 8 hours sit inside the general 7 to 9 hour adult range. Consistent sleep times and waking up feeling rested matter more than the exact number.
Ten PM to 4 AM is 6 hours in bed, which is below the general 7 to 9 hour recommendation for adults, and you will actually sleep a little less because it takes time to fall asleep. A schedule closer to 7.5 hours, such as 10:00 PM to 5:30 AM, suits most adults better.
Eleven PM to 5 AM is 6 hours in bed, which is below the general 7 to 9 hour range for adults. Actual sleep time will be slightly shorter after you fall asleep. Moving to something like 11:00 PM to 6:30 AM gives you about five full cycles.
Yes. The Nap Calculator suggests a wake-up time for a 20-minute power nap, a 30-minute short nap, a 90-minute full-cycle nap or a custom length. Shorter naps tend to cause less grogginess, and naps late in the day can make it harder to fall asleep at night.
Feeling tired after seven or more hours can come from poor sleep quality, irregular sleep times, waking during the night, alcohol or caffeine late in the day, stress, or waking from deep sleep (sleep inertia). Ongoing daytime tiredness can also be linked to medical or sleep conditions, so consider talking with a healthcare professional.
Falling asleep in about 10 to 20 minutes is common for healthy adults, and this calculator uses 15 minutes by default. Falling asleep almost instantly can be a sign you are short on sleep, while regularly taking more than 30 minutes may be worth discussing with a healthcare professional.
It depends on when you need to wake up. Count back 7.5 to 9 hours (five or six cycles) from your wake-up time, then add about 15 minutes to fall asleep. For example, to wake at 6:30 AM you could go to bed around 10:45 PM for five cycles or 9:15 PM for six cycles. Use Bedtime mode to calculate your own times.
It depends on when you go to bed. Add about 15 minutes to fall asleep, then add complete 90-minute cycles, usually five or six. For example, if you get into bed at 11:00 PM you would fall asleep around 11:15 PM and could wake at 6:45 AM after five cycles or 8:15 AM after six. Use Wake-up time mode to calculate yours.