How it is calculated
A popular scheme treats one sleep cycle as 90 minutes and adds 10 to 20 minutes for falling asleep. Real cycles differ from person to person, so the time on the screen is a convenient grid, not a measuring device.
Bedtime = wake-up − cycles × 90 minutes − time to fall asleep
Where the numbers come from
- I know
- Time
- Time to fall asleep — unit in the field: min
Example
Up at 07:00, 15 minutes to fall asleep, 6 cycles. Bedtime is 21:45.
Questions
Why several times?
Each line is the end of the next cycle. Getting up between cycles is often easier than waking in the middle of one.
Can I change the cycle length?
In this version the cycle is fixed at 90 minutes. Only the time to fall asleep can change.
Is this a treatment for insomnia?
No. If sleep has been off for weeks, that is a conversation with a doctor, not with a chart.