Bedtime Calculator

1. Enter your wake-up time. Use the time your alarm goes off, not the time you get out of bed.
2. Set how long you take to fall asleep. Leave 15 minutes if you are not sure. Raise it if you usually lie awake longer.
3. Pick your age group. The calculator then highlights the bedtime that gives you enough full cycles for your age.

The highlighted bedtime is the latest one that still meets the sleep range for your age group.

A bedtime calculator is a planning tool that works backward from a fixed wake-up time to show when you should be in bed. It adds the minutes you need to fall asleep and then subtracts whole sleep cycles, so your alarm is more likely to ring near the end of a cycle than in the middle of deep sleep.

It does not measure your sleep, track stages, or detect a sleep disorder. It turns a wake-up time and a few averages into a bedtime you can act on tonight.

The calculator subtracts your time to fall asleep and a whole number of sleep cycles from your wake-up time. Each cycle moves through light non-REM sleep, deep non-REM sleep, and REM sleep. The NHLBI describes a cycle that repeats every 80 to 100 minutes, four to six times a night, which is why 90 minutes is the usual planning figure.

1. Convert the wake-up time to minutes after midnight (6:30 AM = 390).
2. Subtract the minutes you need to fall asleep (390 – 15 = 375).
3. Subtract 3, 4, 5 and 6 cycles (for example 5 x 90 = 450, so 375 – 450 = -75).
4. Wrap negative values around midnight (-75 + 1,440 = 1,365 minutes = 10:45 PM).
5. Highlight the smallest number of cycles that reaches the minimum sleep for your age group.

Learn what happens inside each cycle in our guide to the stages of sleep.

Maria is 34 and her alarm is set for 6:30 AM. She usually falls asleep in about 15 minutes and has no reason to think her cycles are unusual, so she keeps the 90-minute default.

Five cycles give her 7.5 hours of sleep, which meets the 7-hour adult minimum, so the calculator highlights 10:45 PM. If she stays up to 11:30 PM instead, her alarm lands partway through a cycle.

Time To Fall Asleep

Every extra 15 minutes it takes you to fall asleep pushes the right bedtime 15 minutes earlier.

Cycle Length

Cycles vary from person to person, so the tool accepts 70 to 120 minutes. A longer cycle moves every bedtime earlier.

Age

Teens need 8 to 10 hours and children 6 to 12 need 9 to 12 hours, so the highlighted bedtime moves one cycle earlier for them.

Body Clock And Schedule

Your circadian rhythm decides when you feel sleepy. Night-shift workers should plan around their own shift pattern with the shift work sleep calculator.

These assume 15 minutes to fall asleep and 90-minute cycles. Most adults should pick 5 cycles.

More wake-up times: 4:00 AM, 4:30 AM, 8:30 AM, 9:00 AM, 9:30 AM, 10:00 AM, 10:30 AM, 11:00 AM, 11:30 AM, 12:00 PM, 12:30 PM, 1:00 PM, 1:30 PM, 2:00 PM, 2:30 PM.

If your bedtime is fixed and your alarm is flexible, run the sum forwards.

In bed at 11:00 PM and asleep by 11:15 PM, set the alarm for 6:45 AM (5 cycles) or 8:15 AM (6 cycles). The 90-minute sleep cycle calculator in the related tools below does this for you, including a Right now option.

When the fixed point is an event, not an alarm, choose Early start. The calculator works out your wake-up time first, then counts back in cycles.

Sam has an exam at 9:00 AM. He needs 45 minutes to get ready, 40 minutes to travel and wants 15 spare minutes.

The same steps fit an early flight, a race or a first day at work. If the bedtime is much earlier than usual, your body clock may not feel sleepy yet, so raise the minutes to fall asleep to plan for that.

The original Sleepytime site, sleepyti.me, now redirects to a page that returned an error when we checked in October 2026.

It is most useful when your wake-up time is fixed and your bedtime is flexible.

• Students and parents: set the age group to Teen or Child to see a bedtime with enough cycles for a growing body.
• Travellers and shift workers: use it for the first nights on a new schedule.

Using The Time You Get Into Bed As The Time You Fall Asleep

Lying awake counts. Add your real time to fall asleep or the plan will be short by that amount every night.

Chasing The 3-Cycle Option Every Night

4.5 hours ends on a cycle boundary but is far below what adults need.

Changing Bedtime Every Day

A steady schedule trains your body clock. Pick one bedtime and keep it, weekends included.

Ignoring Sleep Habits

Late caffeine, bright screens and a warm room all delay sleep. The basics in sleep hygiene 101 make any bedtime work better.

The times are exact for the inputs you give, but your real cycles vary from night to night.

Neither is better by itself. 7.5 hours ends on a cycle boundary, while 8 hours gives slightly more sleep. Choose what you can keep every night.

Most tools fix the time to fall asleep and the cycle length. This one lets you change both and applies an age-based minimum.

Count back 8 hours plus your time to fall asleep from your alarm. For a 6:30 AM alarm and 15 minutes to fall asleep, that is 10:15 PM; 10:45 PM gives 7.5 hours and ends on a cycle.

It uses the same idea of counting back in 90-minute cycles, but you can also change time to fall asleep, cycle length and age group.

An average cycle lasts about 90 minutes. The NHLBI describes a range of 80 to 100 minutes, and cycle length varies from person to person.

Most adults need four to six cycles a night. Five cycles of 90 minutes equal 7.5 hours, which meets the NHLBI guidance of 7 to 8 hours for adults.

It can give you a consistent schedule, but it does not treat insomnia. Ongoing trouble sleeping should be checked by a doctor.

No. Short naps follow different rules. Use a nap tool for daytime sleep.

• NHLBI: How much sleep is enough? (age-group sleep ranges)
• NHLBI: Sleep phases and stages (80 to 100 minute cycles, four to six per night)
• NINDS: Brain basics, understanding sleep (circadian rhythm and sleep regulation)
• MedlinePlus: Healthy sleep (sleep habits and when to see a doctor)