Sleep Calculator
Find the best bedtimes or wake-up times based on 90-minute sleep cycles.
What do you want to plan?
Go to bed at one of these times
- 09:45 PM 6 cycles· recommended
- 11:15 PM 5 cycles· recommended
- 12:45 AM 4 cycles
Based on 90-minute cycles plus ~15 minutes to fall asleep. Real cycles vary (~70–120 min); use these times as a guide.
Frequently Asked Questions
How does the sleep calculator work?
It counts backward or forward in 90-minute sleep cycles and adds about 15 minutes to fall asleep. Choose "I want to wake up at" to get suggested bedtimes, or "I am going to bed at" to see when you will wake up. Waking at the end of a cycle, rather than mid-cycle, helps you feel more rested.
How many sleep cycles do I need?
Most adults do best with 5 to 6 cycles (about 7.5 to 9 hours). The calculator highlights the 5- and 6-cycle options as recommended and still shows a 4-cycle option for shorter nights.
Are sleep cycles always exactly 90 minutes?
No. 90 minutes is an average; real cycles vary from person to person and across the night, roughly 70 to 120 minutes. Use the suggested times as a helpful guide rather than a strict rule.