Sleep Calculator
Estimate a recommended bedtime from your wake time and sleep cycles.
Input Data
格式 時:分，例如 07:00。
每週期約 90 分鐘，一般 4–6 個。
Results
23:30
For 5 cycles (450 min) before 07:00
At a glance:Bedtime = wake time − cycles × 90 minutes (rolled back to the previous day if needed).
Formula
bedtime minutes = wake minutes − cycles × 90
roll back to previous day if negative
How to Use
- Enter your wake time and number of cycles.
- Read the suggested bedtime.
FAQ
Why 90 minutes?
A sleep cycle is about 90 minutes; waking at the end of a cycle (light sleep) feels less groggy.
How many cycles?
Adults usually need 4–6 cycles (about 6–9 hours).
Related Tools
References
Content review: Calculatorism Science Team.