Sleep Cycle Calculator
Wake up between sleep cycles, not in the middle of one. Enter your wake time or bedtime — get the optimal alternative.
24-hour format. Allow ~14 min to actually fall asleep.
How to use
- 1
Pick whether you're planning forward from now (going to bed) or backward from a fixed wake time (alarm tomorrow).
- 2
Enter the time in 24-hour format (e.g. 07:00 for 7am, 23:30 for 11:30pm).
- 3
The result shows 4 candidate sleep durations. Each ends at the close of a 90-minute cycle so you wake during light sleep, not deep sleep.
- 4
Even with a perfect calculation, the model is approximate — cycle length varies between people from about 80 to 110 minutes. Use it as a starting point.
Frequently asked questions
A full sleep cycle goes light → deep → REM → light, repeating roughly every 90 minutes. It's an average — actual cycles vary between people from about 80 to 110 minutes. The calculator uses 90 because that's the most common reference.
Healthy adults take about 10-20 minutes to fall asleep. The calculator uses 14 minutes as the average. If you're someone who falls asleep instantly (under 5 minutes), you can mentally subtract a few minutes from the bedtime suggestion.
5-6 cycles (7.5-9 hours) is the standard adult range. 4 cycles (6 hours) is the minimum for one off night without significant cognitive impact. 3 cycles (4.5 hours) is survival mode — fine for one night, not sustainable.
Roughly. The 90-minute cycle model comes from Dement and Kleitman's REM research in the 1950s and remains the standard reference. Real sleep cycles are messier — cycle length, depth, and REM/deep ratios shift through the night and between individuals. Use this as a planning tool, not a clinical instrument.
All four suggestions might land badly. In that case, prioritise total sleep duration (cycles × 90) over hitting a cycle boundary exactly. Sleeping 6 hours but waking at a non-ideal point is still better than sleeping 4.5 hours just to hit the cycle.
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Source: Standard 90-minute sleep cycle model (Dement & Kleitman, REM research) · Last verified 2026-06. This tool provides estimates only and is not legal, tax or financial advice. Always verify your specific situation with the relevant UAE authority or a licensed advisor before taking action.