Sleep Cycle Calculator
Find the best times to go to sleep or wake up in whole sleep cycles.
Results update as you type.
About this calculator
Sleep runs in cycles of roughly 90 minutes, and waking at the end of a cycle rather than the middle leaves you feeling more rested. This calculator works backward from a wake-up time to suggest bedtimes, or forward from a bedtime to suggest wake times, targeting complete 5–6 cycle nights and allowing time to fall asleep.
Frequently asked questions
How long is one sleep cycle?
About 90 minutes on average, moving through light, deep and REM sleep. The calculator aims for whole cycles — typically 5 or 6, i.e. 7.5 to 9 hours — so you wake between cycles rather than mid-cycle.
Why add time to fall asleep?
You do not fall asleep the instant your head hits the pillow. The calculator adds a buffer (15 minutes by default) so the cycle timing is measured from when you actually drift off, not when you get into bed.
Results are estimates for general guidance only, not financial, medical or tax advice.