Sleep Cycle Calculator
Find optimal sleep/wake times
Formula
Each cycle ≈ 90 minutes
Goal: 5-6 complete cycles
Fall asleep: ~15 min average
Sleep Cycles
| 5 cycles | 7.5 hours |
| 6 cycles | 9 hours |
| Light sleep | Stage 1-2 |
| Deep sleep | Stage 3-4 |
| REM | Dreams |
Related
Complete Guide to Sleep Cycle Calculator
Sleep occurs in cycles of approximately 90 minutes, each containing light sleep, deep sleep, and REM (dream) sleep. Waking at the end of a cycle - during light sleep - helps you feel refreshed rather than groggy.
Understanding Sleep Cycles
A complete sleep cycle progresses through stages: light sleep (Stage 1-2), deep sleep (Stage 3-4), and REM sleep. Deep sleep is most restorative for physical recovery, while REM is crucial for memory and learning.
Optimal Sleep Duration
- Adults: 7-9 hours (5-6 cycles)
- Teens: 8-10 hours
- Children: 9-12 hours
Sleep Hygiene Tips
Maintain consistent sleep/wake times. Avoid screens 1 hour before bed. Keep bedroom cool (65-68°F/18-20°C) and dark. Limit caffeine after 2pm. Exercise regularly but not within 3 hours of bedtime.
Why You Feel Groggy
Waking during deep sleep causes sleep inertia - that heavy, groggy feeling. By timing your alarm to the end of a cycle, you're more likely to wake during light sleep and feel alert immediately.
Frequently Asked Questions
About 90 minutes on average, though it can range from 80-120 minutes. The calculator uses 90 minutes as a reliable average. Your cycles may be slightly shorter or longer.
You might be waking mid-cycle during deep sleep. Try sleeping 7.5 hours (5 cycles) or 9 hours (6 cycles) instead. Consistent sleep timing also matters - irregular schedules cause grogginess.
Apps can provide insights but aren't perfectly accurate without clinical equipment. They're useful for tracking trends and consistency. Don't obsess over nightly data - focus on how you feel.
Waking naturally is ideal - it means you completed your sleep cycles. If you consistently wake before your alarm feeling refreshed, your body might need less sleep than you think.
Average is 10-20 minutes. Falling asleep instantly may indicate sleep deprivation. Taking over 30 minutes regularly suggests potential insomnia. This calculator assumes 15 minutes to fall asleep.
Partially. You can recover from short-term sleep debt, but chronic deprivation causes lasting effects. It's better to maintain consistent adequate sleep than to 'bank' or 'repay' sleep.
Brief awakenings are normal and often go unremembered. If you're awake for 20+ minutes, get up and do something relaxing until sleepy. Don't watch the clock - it increases anxiety.