Sleep Calculator

A complete sleep cycle includes light sleep, deep sleep, and REM sleep, taking about 90 minutes. Waking between cycles (not during) helps you feel refreshed. 5 cycles = 7.5 hours, 6 cycles = 9 hours. That's why 7.5 hours often feels better than 8—you wake between cycles.

Adults need 7-9 hours for optimal health. Teenagers: 8-10 hours. Children (6-12): 9-12 hours. Sleep needs vary individually—some thrive on 7, others need 9. Signs of inadequate sleep: daytime drowsiness, difficulty concentrating, mood changes, weakened immunity.

Count backward in 90-minute cycles plus 15 minutes to fall asleep. For 7am wake-up: 5 cycles = 11:15pm, 6 cycles = 9:45pm. Choose 9:45pm (9 hours) or 11:15pm (7.5 hours) based on your needs. Avoid 10:45pm (8.25 hours)—you'd wake mid-cycle.

Yes. Snooze sleep is fragmented and low-quality. You start a new sleep cycle you won't finish, causing grogginess (sleep inertia). Better approach: set your alarm for when you need to get up, place it across the room, and get up immediately. Consistency helps your body wake naturally.

Proven techniques: Keep a consistent schedule (even weekends). Avoid screens 1 hour before bed (blue light suppresses melatonin). Keep room cool (65-68°F/18-20°C). Limit caffeine after 2pm. Try the 4-7-8 breathing technique. If you can't sleep after 20 minutes, get up briefly rather than lying awake frustrated.