Sleep Calculator
Find the best bedtimes based on 90-minute sleep cycles so you wake up feeling refreshed.
Waking up groggy and tired often isn't about how long you sleep, but when you wake up within your sleep cycle. Each sleep cycle lasts approximately 90 minutes and consists of light sleep, deep sleep, and REM sleep stages. Waking between cycles — rather than in the middle of one — helps you feel alert and refreshed.
This calculator works backward from your desired wake-up time, subtracting 90-minute sleep cycles plus 15 minutes to fall asleep. It provides four bedtime options ranging from 3 to 6 complete cycles.
Most adults need 5-6 sleep cycles (7.5-9 hours) per night for optimal health and cognitive performance. Consistently getting fewer than 6 hours is associated with increased risks of obesity, heart disease, diabetes, and impaired immune function.
For the best sleep quality, maintain a consistent sleep schedule (even on weekends), keep your room cool and dark, avoid screens 30-60 minutes before bed, and limit caffeine after 2 PM. Your body's internal clock (circadian rhythm) works best with regularity.