Sleep Cycle Calculator
Find the best bedtimes or wake times based on 90-minute sleep cycles.
Results update as you type.
About this calculator
A sleep calculator suggests bedtimes or wake-up times aligned to 90-minute sleep cycles, so you wake between cycles rather than in the middle of deep sleep and feel more refreshed. It counts back or forward in 90-minute blocks and adds the time it takes to fall asleep. Most adults do best on five to six complete cycles (7.5–9 hours).
Frequently asked questions
How long is a sleep cycle?
About 90 minutes. A full night moves through four to six of these cycles, each passing from light to deep to REM sleep. Waking at the end of a cycle, rather than mid-cycle, tends to feel less groggy.
How many sleep cycles do I need?
Most adults feel best with five to six complete cycles — roughly 7.5 to 9 hours. The calculator highlights those options and lists shorter ones for a nap or a late night.
Why add time to fall asleep?
You do not sleep the instant you lie down. Adding an average 15 minutes of sleep-onset time makes the suggested bedtime line up with when you actually start cycling through sleep.
Results are estimates for general guidance only, not financial, medical or tax advice.