Sleep Cycle Calculator
Find the best times to go to bed or wake up so you wake between 90-minute sleep cycles and feel less groggy.
For general information only — not medical advice. Results are estimates; talk to a doctor or qualified health professional about your own health.
How to use
- 1Choose whether you know your wake-up time or your bedtime.
- 2Pick one of the suggested times — 5 or 6 cycles is ideal for most adults.
How it's calculated
One sleep cycle ≈ 90 minutes; falling asleep takes about 15 minutes. Bedtimes = wake time − 15 min − n × 90 min.
Frequently asked questions
How much sleep do adults need?
7–9 hours a night for most adults (American Academy of Sleep Medicine / NHS). Teens need 8–10.
Are sleep cycles always 90 minutes?
They range from about 70 to 120 minutes and vary through the night, so treat these times as a guide.
Why do I feel groggy after a long sleep?
Waking from deep sleep in the middle of a cycle causes sleep inertia. Waking at the end of a cycle is usually easier.