XP TRACKERSleep calculator: bedtime and wake-up times
To wake at 7:00 after five 90-minute cycles, aim to be in bed around 23:15, which leaves about 15 minutes to fall asleep. Enter your wake-up time or your bedtime and the calculator lists the times that line up with full cycles.
Find your times
How the calculator works
Sleep runs in cycles of lighter and deeper stages, often around 90 minutes each. Waking near the end of a cycle, in lighter sleep, can feel easier than being pulled out of deep sleep. The calculator counts back from your wake-up time in whole cycles and adds the time it usually takes to fall asleep.
The formula: bedtime = wake time - (cycles x cycle length) - time to fall asleep. For a 7:00 alarm with five 90-minute cycles and 15 minutes to drift off: 7:00 - 7 h 30 min - 15 min = 23:15.
If you choose "going to bed now" or enter a bedtime, it counts forward instead and suggests alarm times.
Pick enough sleep first
Cycles are a fine-tuning trick. The bigger question is total sleep. A 2015 consensus statement from the American Academy of Sleep Medicine and the Sleep Research Society recommends that adults sleep 7 or more hours a night regularly. That usually means five cycles (7.5 hours) or six (9 hours). The calculator marks shorter options so you can see the trade-off.
Limits of the cycle idea
Cycles are not clockwork. They commonly range from about 70 to 120 minutes, they shift across the night, and your time to fall asleep changes from one night to the next. Treat the times as a starting point. If you wake up groggy every day at one time, try moving your alarm 15 minutes earlier or later for a week and see how it feels.
Small habits that make bedtime easier
- Keep the wake-up time steady, weekends included, within about an hour. A fixed morning helps your body know when to get sleepy at night.
- Set a "start winding down" alarm 30 to 45 minutes before your bedtime, not just a wake-up alarm.
- Get daylight in the morning and keep evening light dim.
- Watch late caffeine. Many people sleep better with no coffee after midday.
For a full wind-down, see our evening routine guide and the habit page on going to bed early. If you want to shift your wake time earlier, the wake-up time planner does it in small steps.
This tool is not medical advice. If you snore loudly, stop breathing in your sleep, feel very sleepy in the day, or cannot sleep most nights, talk to a doctor.
Try it tonight
Enter tomorrow's alarm time, pick the five-cycle bedtime, and set a wind-down alarm 30 minutes before it.
Questions people ask
What time should I go to bed if I wake up at 6?
For five 90-minute cycles (7.5 hours) plus 15 minutes to fall asleep, about 22:15. For six cycles (9 hours), about 20:45. Four cycles would mean about 23:45, but that is only 6 hours, less than most adults need.
How long is a sleep cycle?
Often around 90 minutes, but cycles commonly range from about 70 to 120 minutes and change through the night and between people. That is why the calculator lets you change the cycle length.
How much sleep do adults need?
Adults generally need 7 or more hours a night on a regular basis, according to a 2015 consensus statement from the American Academy of Sleep Medicine and the Sleep Research Society. Some people need more.
Is it better to sleep 6 hours or 7 and a half?
For most adults, 7 and a half. Waking at the end of a cycle may feel easier, but it does not make up for too little sleep overall. Total sleep matters more than hitting a cycle boundary.
Why do I wake up tired even after 8 hours?
Many things can cause it: irregular sleep times, alcohol or caffeine late in the day, a noisy or warm room, stress, or a sleep disorder such as sleep apnoea. If you feel tired most days despite enough time in bed, talk to a doctor.
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