About this calculator

A sleep calculator suggests bedtimes or wake times using ~90-minute sleep cycles plus fall-asleep buffer.

Who should use it: People planning schedules around typical sleep cycles.

When to use it: Use it to pick candidate bed/wake times — individual needs vary.

Sleep cycle timing

Each sleep cycle is modeled as 90 minutes. A fall-asleep buffer is added so cycles start after you actually fall asleep.

Step-by-step

1. 1

   Choose what you know

   Pick a fixed wake time or a fixed bedtime.

2. 2

   Enter the clock time

   Use 24-hour hour (0–23) and minute (0–59).

3. 3

   Set fall-asleep minutes

   Typical values are 10–20 minutes.

4. 4

   Review cycle options

   Compare 6, 5, 4, and 3 cycle suggestions.

Worked example: Wake at 07:00

Wake-at mode for 07:00 with a 14-minute fall-asleep buffer.

1. 6 cycles = 540 minutes of sleep
2. Add 14 minutes to fall asleep → 554 minutes before 07:00
3. Bedtime ≈ 21:46

Best 6-cycle bedtime is 21:46.

How to interpret the result

Waking near a cycle boundary may feel easier for some people; it is a heuristic, not a clinical sleep study.

Key definitions

Sleep cycle

A repeating stage pattern commonly approximated as 90 minutes.

Fall-asleep buffer

Minutes between lights out and actually falling asleep.

Cycle count

Number of full 90-minute cycles in the sleep opportunity.

Common use cases

• Planning a school or work wake time
• Choosing a bedtime after a late evening
• Napping with cycle awareness

Tips

• If you wake groggy, try a neighboring cycle suggestion.
• Keep a consistent schedule when possible — calculators help, habits matter more.

Common mistakes

Limitations

• Not a diagnosis or treatment for sleep disorders.
• Cycle length varies by person and night.