😴 Sleep Calculator

Find the best time to wake up or go to sleep based on your natural sleep cycles.

What do you want to calculate?

Time you are going to sleep

Enter the time

How does this sleep calculator work?

Sleep is organised in cycles of approximately 90 minutes each. Each cycle includes light sleep, deep sleep and REM sleep stages. Waking up at the end of a complete cycle — during light sleep — makes you feel much more refreshed than waking up in the middle of deep sleep, even if you slept fewer hours total.

This calculator adds 15 minutes to account for the average time it takes to fall asleep. Most adults need 5 to 6 complete cycles (7.5 to 9 hours) per night for optimal rest.

Frequently asked questions

How many hours of sleep do I need?

Most adults need 7–9 hours per night (5–6 sleep cycles). Teenagers need 8–10 hours. Children need more. Quality matters as much as quantity.

What time should I go to sleep to wake up at 7am?

To wake up at 7:00 AM feeling refreshed, the ideal bedtimes are 9:45 PM (6 cycles), 11:15 PM (5 cycles), 12:45 AM (4 cycles) or 2:15 AM (3 cycles).

Why do I feel groggy even after 8 hours of sleep?

Probably because your alarm woke you up in the middle of a deep sleep cycle. Try adjusting your wake-up time by 15–30 minutes to land at the end of a cycle.