Sleep Calculator
Sleep cycles run about 90 minutes. Waking at the end of a cycle (rather than mid-cycle) helps you feel more rested. Enter when you want to wake up or go to bed to find the best times.
Sleep Calculator
Find cycle-aligned bedtimes and wake times
Sleep cycles are ~90 minutes. Aim for 4–6 cycles per night plus ~15 minutes to fall asleep. Best times align with cycle boundaries.
How Sleep Cycles Work
Sleep isn't uniform — it cycles through stages roughly every 90 minutes (light → deep → REM). Waking at the end of a cycle (during lighter sleep) typically feels better than being woken mid-cycle during deep sleep.
A full night's sleep usually includes 4–6 cycles. Allow about 15 minutes to fall asleep.
**Example**: To wake at 7:00 AM with 5 cycles (7.5 hours of sleep), go to bed around 11:15 PM (7:00 − 7.5 hours − 15 minutes).
- Sleep cycle ≈ 90 minutes
- 4–6 cycles per night is typical
- Add ~15 minutes to fall asleep
- Wake at cycle end feels more rested
Worked Example
Example: You need to wake at 6:30 AM.
- 6 cycles (9 hours): bedtime ≈ 8:45 PM - 5 cycles (7.5 hours): bedtime ≈ 10:15 PM - 4 cycles (6 hours): bedtime ≈ 11:45 PM - Each option adds ~15 minutes to fall asleep.
Choose the bedtime you can realistically meet — consistency matters more than hitting an exact cycle.
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Open calculator →Frequently Asked Questions
Does everyone have 90-minute cycles?
Roughly. Cycle length varies person to person and across the night (early cycles have more deep sleep, later cycles more REM). 90 minutes is the average used by most sleep calculators.
Is 6 hours enough sleep?
Most adults need 7–9 hours. Regularly sleeping 6 hours or less is linked to poorer health and performance for most people, even if it feels fine short-term.
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