HEALTH · SLEEP CYCLE
Sleep Cycle Calculator
Find the best time to go to sleep or wake up based on 90-minute sleep cycles. Uses sleep-onset latency to recommend times that complete full REM cycles.
Assumes 14-minute sleep onset. Results are estimates — individual sleep patterns vary.
About This Calculator
This sleep cycle calculator helps you plan the best time to go to sleep or wake up by aligning with your natural 90-minute sleep cycles. Enter your target wake time or bedtime to see recommended options that let you complete full cycles and wake up feeling refreshed.
How It Works
A complete sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Waking at the end of a cycle — rather than in the middle — reduces grogginess. The calculator also accounts for the average 14-minute sleep-onset latency (how long it takes to fall asleep).
The Formula
Bedtime = Wake time − Sleep-onset latency (14 min) − (Cycles × 90 min). Wake time = Bedtime + Sleep-onset latency (14 min) + (Cycles × 90 min). Results are shown for 4, 5, and 6 full cycles.
Frequently Asked Questions
- How long is a sleep cycle?
- One complete sleep cycle lasts approximately 90 minutes and progresses through light sleep (N1, N2), deep sleep (N3), and REM sleep. Most adults complete 4–6 cycles per night.
- Why 14 minutes for sleep onset?
- Research suggests the average person takes about 10–20 minutes to fall asleep after lying down. This calculator uses 14 minutes as a middle estimate. If you fall asleep faster or slower, shift your bedtime accordingly.
- Is 4 cycles (6 hours) enough sleep?
- Most adults need 7–9 hours of sleep per night (5–6 cycles). Four cycles may be sufficient for short-term situations, but consistently sleeping less than 7 hours is associated with impaired cognitive function and health risks.