A full sleep cycle averages around 90 minutes, moving through lighter and deeper stages. Waking at the end of a cycle often feels easier than waking from deep sleep.

How many cycles should I aim for?

Many adults do well with 4 to 6 cycles (about 6 to 9 hours of sleep) plus time to fall asleep. Individual needs differ; track how you feel and adjust.

Does the calculator account for time to fall asleep?

Yes. A default 15 minutes is added before the first cycle. You can change this if you usually fall asleep faster or slower.

Can I use this for shift work?

You can use the same math for any wake time, but shift work challenges circadian rhythm. Bright light, dark bedrooms and consistent routines help; occupational health guidance may be needed.

Last updated: 01.05.2026

Sleep Calculator

Plan bedtime from your wake-up time using 90-minute sleep cycles. Wake between cycles to feel less groggy.

Bedtime options

24h time, e.g. 07:00

21:45 — 6 cycles (~540 min sleep)
23:15 — 5 cycles (~450 min sleep)
00:45 — 4 cycles (~360 min sleep)

Sleep cycles and waking up

Enter the time you need to wake up (24-hour format). The calculator suggests several bedtimes that align with four, five or six full 90-minute cycles, plus a small buffer for falling asleep. Waking at a lighter stage can reduce “sleep inertia” that heavy alarm clocks sometimes worsen.

This is a heuristic, not a medical sleep study. Some people need more deep sleep early in the night; others nap. Experiment and note energy levels across a week.

Better sleep hygiene alongside timing

Consistent sleep and wake times, reduced late caffeine, dim screens before bed, a cool dark room and morning daylight exposure all support circadian alignment. If you snore loudly or stop breathing at night, discuss sleep apnoea screening with a clinician.

For travel across time zones, pair this tool with a jet lag plan that includes light exposure and gradual schedule shifts.