What this calculator does
Sleep quality depends on duration, consistency and uninterrupted cycles. Adults are generally advised to get 7–9 hours per night.
This calculator uses bedtime, wake time and sleep latency to estimate net sleep and the number of 90-minute cycles. It also suggests bedtimes for four, five or six cycles.
Sleep duration
Net sleep = wake time − bedtime (+24 h across midnight) − sleep latency If wake time is earlier than bedtime, 24 hours are added. Cycle count is net sleep divided by 90 minutes.
How this calculator works
- 01
Enter your times
Choose bedtime and wake time; overnight spans are handled automatically.
- 02
Adjust sleep latency
Add how many minutes it usually takes you to fall asleep.
- 03
Compare cycle times
Review the current duration against recommended cycle-based bedtimes.
Practical tips
- Keep similar sleep times on weekends.
- Reduce afternoon caffeine and dim screens before bed.
Frequently asked questions
How much sleep do I need?
Most adults need 7–9 hours, and older adults often 7–8. Feeling rested and functional during the day matters more than a fixed number.
Is a sleep cycle always 90 minutes?
No. Cycles typically last 70–120 minutes; 90 minutes is an average used for planning.
Does waking at the end of a cycle help?
It may reduce sleep inertia for some people, but the effect is individual and does not replace good sleep habits.
Data basis: 2026 · Annual constants live in structured JSON files and are updated once a year.
Results are unverified model calculations and do not replace tax, legal or financial advice.