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Sleep calculator: when to go to bed

Waking up in the middle of a sleep cycle makes you groggy. Enter when you want to wake up – or when you go to bed – to see times that fit full sleep cycles.

I want to
Time to fall asleep
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How to use the sleep calculator

  1. Choose whether you know your wake-up time or your bedtime.
  2. Enter the time and how long you usually take to fall asleep (about 15 minutes for most people).
  3. Pick one of the suggested times. Five or six cycles (7.5–9 hours) are recommended for adults.

How it works

During the night you go through cycles of light, deep and REM sleep that last about 90 minutes on average. Waking at the end of a cycle, when sleep is lightest, usually feels easier than waking from deep sleep.

Bedtime = wake-up time − time to fall asleep − cycles × 90 min

Worked example

To wake at 7:00 am and fall asleep in 15 minutes, go to bed at 9:45 pm (6 cycles, 9 hours), 11:15 pm (5 cycles, 7.5 hours) or 12:45 am (4 cycles, 6 hours). If you go to bed at 11:00 pm, the best alarm times are 6:45 am or 8:15 am.

How much sleep do adults need?

Health organisations recommend at least 7 hours a night for adults; teenagers need 8–10. Cycle length varies from about 70 to 120 minutes between people and nights, so treat the times as a guide and adjust after a few days.

If you regularly feel tired despite enough sleep, snore loudly or struggle to sleep, talk to a doctor.

Frequently asked questions

How long is a sleep cycle?
About 90 minutes on average, though it can range from roughly 70 to 120 minutes.
What time should I go to bed to wake up at 6 am?
With 15 minutes to fall asleep: 8:45 pm (9 hours), 10:15 pm (7.5 hours) or 11:45 pm (6 hours).
Is 6 hours of sleep enough?
For most adults, no. At least 7 hours is recommended; regularly sleeping 6 hours or less is linked to poorer concentration and health.

Last reviewed: November 13, 2026

Results are estimates for general information only and are not financial, tax, medical or legal advice. Check important figures with a qualified professional.