Sleep Cycle Calculator
Wake up between sleep cycles, not in the middle of one. Pick a time and get your options.
Bedtimes below already include ~15 minutes to fall asleep.
Not medical advice. This tool gives a general estimate for informational purposes only — it does not replace professional judgment. If you're concerned, contact a doctor right away. This is sleep-cycle arithmetic based on population averages, not a clinical measurement of your own cycles — real cycles vary by person and night. If you regularly struggle to fall asleep, stay asleep, or feel unrested, talk to a doctor or sleep specialist.
How this works & sources
Sleep runs in cycles of roughly 90 minutes, each moving from light sleep down into deep sleep and REM and back toward light sleep. Waking at the end of a cycle — in light sleep — tends to feel easier than being pulled out of deep sleep mid-cycle. This calculator counts back (or forward) in 90-minute blocks and adds about 15 minutes to fall asleep, so each suggested time lands on a cycle boundary.
The 90-minute cycle length and the ~15-minute fall-asleep estimate come from the Sleep Foundation's "Stages of Sleep" and the National Sleep Foundation. A typical night is 4–6 complete cycles.
One honest caveat: cycle length isn't exactly 90 minutes for everyone, and it shifts across the night and with age, alcohol, and recent sleep. Treat these as helpful targets, not a precise readout of your own sleep — and prioritise getting enough total sleep over hitting an exact cycle boundary.