Sleep Cycle & Bedtime Calculator
Calculate ideal wake-up times and bedtime schedules based on natural 90-minute sleep cycles.
The time you actually get up.
The average adult takes around 14 minutes.
Wind down with the same sound every night
Momental pairs a bedtime routine with 100+ soundscapes and timers on iPhone and Android.
Get MomentalHow to use the sleep cycle calculator
- 1
Pick the question you are answering. Wake-up time works backwards from your alarm to tell you when to go to bed. Go to sleep now works forwards from this moment to tell you when to set the alarm.
- 2
Enter your alarm time. Use the time you actually get up, not the first snooze. The calculator counts back from that moment in whole 90-minute cycles.
- 3
Set how long you take to fall asleep. Fourteen minutes is the average. If you regularly lie awake for half an hour, choose 30 — this offset is what makes the result land on a real cycle boundary.
- 4
Choose a highlighted time. Five and six cycles (7.5 and 9 hours) are the recommended options for adults. Four cycles works for a short night, three only as a fallback.
- 5
Start your wind-down at that time. The suggested time is when your head hits the pillow, not when you start brushing your teeth. Begin dimming lights and turning on sound around 30 minutes earlier.
How 90-minute sleep cycles work
Sleep runs in repeating cycles of roughly 90 minutes. Each one moves through light NREM stages, deep slow-wave sleep, and finally REM, where most dreaming happens — then starts again.
An alarm that fires in the middle of deep sleep produces sleep inertia: the heavy, disoriented feeling that can last well past your first coffee. Landing the alarm near the end of a cycle, when sleep is lightest, is what makes the same amount of sleep feel dramatically better.
Ninety minutes is an average, not a rule — real cycles run from about 70 to 120 minutes and lengthen through the night. Treat the suggested times as a target window rather than an exact instruction.