Find the ideal time to go to sleep or wake up based on 90-minute sleep cycles. Wake up at the end of a cycle to feel refreshed instead of groggy.
Hour
Min
Assumes ~15 minutes to fall asleep. 5-6 cycles (7.5-9 hours) is ideal for most adults.
Each 90-minute cycle includes light sleep, deep sleep, and REM phases
Light Sleep
~50%
of each cycle
Deep Sleep
~25%
body restoration
REM Sleep
~25%
memory & dreams
Visual clock showing your sleep window (5-cycle recommendation)
Each sleep cycle progresses through these stages
Awake
5 min
Falling asleep
Stage 1
5 min
Light transition
Stage 2
25 min
Light sleep
Stage 3
20 min
Deep / slow-wave
Stage 2
15 min
Light sleep
REM
20 min
Dreaming / memory
National Sleep Foundation guidelines compared to your selection
Newborn (0-3 mo)
14-17
hours/night
Infant (4-11 mo)
12-15
hours/night
Toddler (1-2)
11-14
hours/night
Preschool (3-5)
10-13
hours/night
School (6-13)
9-11
hours/night
Teen (14-17)
8-10
hours/night
Adult (18-64)
7-9
hours/night
MatchSenior (65+)
7-8
hours/night
MatchSleep is not a uniform state — your brain cycles through distinct stages approximately every 90 minutes. Each cycle includes light sleep, deep sleep, and REM (dream) sleep. Waking up during deep sleep causes sleep inertia, that groggy, disoriented feeling. By timing your alarm to the end of a complete cycle, you can wake up during light sleep and feel significantly more alert, even with fewer total hours of sleep.
A sleep cycle is a roughly 90-minute period that includes all stages of sleep: light sleep (N1, N2), deep sleep (N3), and REM sleep. Most adults go through 4-6 complete cycles per night. Waking up at the end of a cycle, during light sleep, helps you feel more refreshed.
Most adults need 7-9 hours of sleep per night (4-6 sleep cycles). Teenagers need 8-10 hours, school-age children need 9-12 hours, and toddlers need 11-14 hours. Individual needs can vary, but consistently getting less than 7 hours is associated with health risks.
You may be waking up in the middle of a deep sleep stage rather than at the end of a complete cycle. This calculator helps you time your sleep so you wake during light sleep. Other factors include poor sleep quality, sleep disorders, inconsistent sleep schedule, or consuming caffeine or alcohol before bed.
Water Intake Calculator
Find out how much water you should drink daily based on your weight, activity level, and climate. Get your personalized hydration goal in liters, ounces, and cups.
BMI Calculator
Calculate your Body Mass Index (BMI) using your height and weight. Supports both imperial and metric units with color-coded health category results.