Question 1

How does the sleep calculator work?

Accepted Answer

Based on the 90-minute sleep cycle (light sleep + deep sleep + REM). Adults need 5-6 complete cycles (7.5-9 hours). Enter your target wake time, and the tool works backwards N cycles of 90 minutes each, plus 15 minutes to fall asleep, to find the best bedtime. Example: wake at 7:00 AM = 6 cycles back + 15 min = go to bed at 9:45 PM.

Question 2

How much sleep do children need?

Accepted Answer

Recommended sleep varies by age: newborns 14-17 hours, toddlers (1-2 yrs) 11-14 hours, preschoolers (3-5 yrs) 10-13 hours, school-age (6-13 yrs) 9-11 hours, teens (14-17 yrs) 8-10 hours, adults 7-9 hours. This tool uses the adult 90-minute cycle; consult a pediatrician for children.

Question 3

What is REM sleep?

Accepted Answer

REM (Rapid Eye Movement) is the 4th stage of sleep where the brain is active, eyes move rapidly under the lids, and most dreaming occurs. A 90-minute cycle includes 4 stages: N1 (light), N2 (intermediate), N3 (deep), and REM. REM accounts for 20-25% of total sleep and is critical for memory consolidation and emotional regulation.

Question 4

How does the 90-minute sleep cycle calculator work?

Accepted Answer

Use this calculator sleep tool: enter any bedtime or wake time and the app cycles backwards (or forwards) through 4-6 complete 90-minute sleep cycles plus 15 minutes to fall asleep. Adults do best with 5-6 cycles (~7.5-9 hours total) for full deep sleep and REM. Cycles vary slightly per person (70-110 minutes), so treat 90 minutes as a planning average, not a strict rule.

Question 5

Is the 90-minute sleep cycle accurate?

Accepted Answer

90 minutes is the average cycle length, but actual cycles range from 70-110 minutes. This tool uses the standard 90 minutes and works well for regular schedules. If you have poor sleep quality (insomnia), calculate based on actual sleep duration rather than 90-minute multiples.

Question 6

What is a sleep pattern calculator?

Accepted Answer

A sleep pattern calculator analyzes your recent sleep logs (bedtime, wake time, quality) to determine your sleep cycle distribution. It can tell you whether you're a "morning lark" or "night owl" and help you optimize your schedule. This tool focuses on the simpler question: given a wake-up or bedtime, what are the best 4-6 complete 90-minute cycles to aim for?

Sleep Calculator

Best Bedtime

Best Bedtime