😴 Sleep Calculator

Find the ideal bedtime or wake-up time based on 90-minute sleep cycles so you wake up feeling refreshed.

Wake-up Time

Based on 90-minute sleep cycles + ~14 minutes to fall asleep. Recommended: 5–6 cycles (7.5–9 hours).

How does the Sleep Calculator work?

Sleep occurs in 90-minute cycles. Waking up at the end of a complete cycle — rather than in the middle — means you wake up naturally during light sleep, feeling more rested and alert. This calculator adds 14 minutes (average time to fall asleep) to help you hit those cycle endpoints.

6 cycles = 9 hours — Maximum recovery, ideal for weekends or after illness
5 cycles = 7.5 hours — Optimal for most adults
4 cycles = 6 hours — Minimum for most people to function well
3 cycles = 4.5 hours — Short-term only; not recommended regularly

How many hours of sleep do adults need?▾

Most adults need 7–9 hours of sleep per night (5–6 full sleep cycles). Teens typically need 8–10 hours, and school-age children need 9–11 hours.

Why do I feel groggy even after 8 hours?▾

You may be waking up mid-cycle (sleep inertia). Using this calculator to align your alarm with the end of a sleep cycle can dramatically reduce morning grogginess.

What time should I go to sleep?▾

Enter your required wake-up time above to see the ideal bedtimes. For a 7:00 AM wake-up, the recommended bedtimes are 9:46 PM (6 cycles) or 11:16 PM (5 cycles).

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