The Sleep Calculator suggests bedtimes or wake times using a 90-minute sleep-cycle assumption and an adjustable time to fall asleep.
Choose wake mode to count cycles backward from a target wake time, or sleep mode to count cycles forward from bedtime. The component suggests three through six cycles.
Limitations
Sleep cycles vary by person and night. The result is not medical advice and does not diagnose sleep disorders or prescribe a schedule.
Method
The calculator treats one sleep cycle as 90 minutes and adds the selected time-to-fall-asleep buffer. Wake mode subtracts complete cycles from a target wake time; sleep mode adds cycles to bedtime. This is clock-time arithmetic, not a measurement of individual sleep architecture.
Example
With a 7:00 a.m. wake time, a 15-minute fall-asleep buffer, and five cycles, the suggested bedtime is about 11:15 p.m. Four cycles gives about 12:45 a.m. These are starting points, not guarantees of sleep quality.
Interpretation
Consistent wake time and adequate total sleep generally matter more than hitting an exact cycle boundary. Discuss persistent insomnia, loud snoring, gasping, or unrefreshing sleep with a clinician.
Common questions
Is every cycle exactly 90 minutes?
No. Cycle length varies across people and across the night; 90 minutes is a planning assumption.
How many cycles should adults target?
The tool shows three to six cycles, but many adults need roughly seven to nine hours. Use personal and clinical guidance.