What is a sleep cycle?

A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Most adults need 4-6 complete cycles (6-9 hours) per night.

Why wake between cycles?

Waking during deep sleep causes grogginess (sleep inertia). Timing your alarm to the end of a complete cycle helps you wake feeling refreshed.

How long does it take to fall asleep?

The average person takes 15 minutes to fall asleep. This calculator adds 15 minutes to the suggested bedtimes to account for this.

How many hours of sleep do adults need?

Most adults need 7-9 hours. The sweet spot for most people is 5 cycles (7.5 hours) or 6 cycles (9 hours). 4 cycles (6 hours) is the minimum.

Sleep Calculator

Calculate optimal bedtimes based on your wake-up time and 90-minute sleep cycles for better rest.

Wake Up Hour

Wake Up Minute

6 Cycles (9h)

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5 Cycles (7.5h) —

4 Cycles (6h) —

3 Cycles (4.5h) —

Extended More scenarios, charts & detailed breakdown ▾

Wake Up Hour

Wake Up Minute

6 Cycles (9h) – Best

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5 Cycles (7.5h) – Good —

4 Cycles (6h) – Minimum —

3 Cycles (4.5h) – Avoid —

Professional Full parameters & maximum detail ▾

Wake Up Hour

Wake Up Minute

Age ?

years

Chronotype

Preferred Cycles

Personalized Recommendation

Recommended Bedtime —

Sleep Duration —

Age-Based Recommendation —

Bedtime Options

Option: 6 Cycles (9h) —

Option: 5 Cycles (7.5h) —

Option: 4 Cycles (6h) —

Sleep Architecture

Est. REM Sleep —

Est. Deep Sleep —

How to Use This Calculator

Enter your desired wake-up time (hour and minute in 24-hour format). The calculator suggests 4 bedtimes based on completing 3, 4, 5, or 6 full 90-minute sleep cycles, plus 15 minutes to fall asleep.

Formula

Bedtime = Wake Time - (Cycles × 90 minutes) - 15 minutes to fall asleep

6 cycles = 9h 15min | 5 cycles = 7h 45min | 4 cycles = 6h 15min | 3 cycles = 4h 45min

Example

Example: Wake at 7:00 AM: Ideal bedtimes are 9:45 PM (6 cycles), 11:15 PM (5 cycles), 12:45 AM (4 cycles), or 2:15 AM (3 cycles).

Frequently Asked Questions

A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Most adults need 4-6 complete cycles (6-9 hours) per night.
Waking during deep sleep causes grogginess (sleep inertia). Timing your alarm to the end of a complete cycle helps you wake feeling refreshed.
The average person takes 15 minutes to fall asleep. This calculator adds 15 minutes to the suggested bedtimes to account for this.
Most adults need 7-9 hours. The sweet spot for most people is 5 cycles (7.5 hours) or 6 cycles (9 hours). 4 cycles (6 hours) is the minimum.

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Sources & References (5) ▾

Watson NF et al. — Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843-844 — AASM / Sleep Research Society
Hirshkowitz M et al. — National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43 — Sleep Health / NSF
Carskadon MA & Dement WC — Normal human sleep: an overview. In: Principles and Practice of Sleep Medicine, 5th ed. 2011 — Sleep Foundation
NIH — Brain Basics: Understanding Sleep — NIH / NINDS
CDC — Are You Getting Enough Sleep? — CDC