Sleep Calculator

Find ideal bedtimes based on 90-minute sleep cycles so you wake up refreshed

Allow ~15 min to fall asleep

07:00 − (15 min + n × 90 min)
Suggested bedtimes
21:45★ Ideal
6 cycles
9h 0m
23:15★ Ideal
5 cycles
7h 30m
00:45
4 cycles
6h 0m
02:15
3 cycles
4h 30m
07:00IdealOne sleep cycle ≈ 90 minutes

About this calculator

The Sleep Calculator helps you find the best bedtime or wake-up time based on 90-minute sleep cycles. Getting up between cycles instead of in the middle of one leaves you feeling more refreshed and alert. Enter your desired wake-up time or bedtime to see sleep-cycle-aligned suggestions.

Common examples

  • Wake at 7:00 AM → suggested bedtimes: 11:00 PM (6 cycles), 12:30 AM (5 cycles), 4:00 AM (2 cycles), 5:30 AM (1 cycle)
  • Bedtime 11:00 PM → suggested wake times: 12:30 AM (1 cycle), 2:00 AM (2 cycles), 5:30 AM (5 cycles), 7:00 AM (6 cycles)
  • Need 7.5 hours of sleep → 5 complete sleep cycles; sleep at 11:00 PM, wake at 6:45 AM
  • Power nap: 1 sleep cycle = 90 min; 2 cycles = 3 hours for a restorative rest
  • Teen needing 9 hours: bedtime 9:30 PM → wake at 6:45 AM (6 complete cycles)