Question 1

How does the sleep calculator work?

Accepted Answer

Our calculator uses the science of sleep cycles. Each complete sleep cycle lasts approximately 90 minutes and includes all stages of sleep (light, deep, and REM). By timing your sleep to complete full cycles, you wake up at the lightest sleep stage, feeling more refreshed rather than groggy.

Question 2

Why is 90 minutes significant for sleep?

Accepted Answer

90 minutes is the average duration of a complete sleep cycle for adults. During this time, you progress through all sleep stages: N1 (light sleep), N2 (light sleep), N3 (deep sleep), and REM (dream sleep). Waking at the end of a cycle means you're in lighter sleep and will feel more alert.

Question 3

How many sleep cycles do I need?

Accepted Answer

Most adults need 5-6 complete sleep cycles (7.5-9 hours) for optimal rest. However, some people function well on 4 cycles (6 hours) while others need 6 cycles (9 hours). Our calculator shows you multiple options so you can find what works best for you.

Question 4

Why do you add 14 minutes to fall asleep?

Accepted Answer

On average, it takes a healthy adult about 14 minutes to fall asleep. We factor this into our calculations so the times shown account for the transition from wakefulness to sleep. If you consistently fall asleep faster or slower, you can adjust this in the personalization settings.

Question 5

Will the browser alarm work if I close the tab?

Accepted Answer

No, the browser alarm only works while this website is open in your browser. If you close the tab, switch browsers, or turn off your computer, the alarm will not sound. For critical wake-up alarms, we recommend using your phone's native alarm app.

Question 6

What if I'm a shift worker with irregular hours?

Accepted Answer

The calculator works for any schedule! Simply enter your desired wake time or sleep time regardless of whether it's day or night. The sleep cycle science remains the same. Shift workers may benefit from extra consistency on their days off to help maintain circadian rhythm.

Question 7

Is this calculator suitable for children?

Accepted Answer

This calculator is designed for adults. Children and teenagers have different sleep needs and cycle lengths. Children typically need 9-11 hours of sleep, while teenagers need 8-10 hours. Consult a pediatrician for guidance on your child's specific sleep needs.

Question 8

How can I improve my sleep quality?

Accepted Answer

Key tips include: maintaining a consistent sleep schedule, avoiding screens 1 hour before bed, keeping your bedroom cool and dark, limiting caffeine after noon, exercising regularly (but not too close to bedtime), and creating a relaxing bedtime routine. Visit our blog for more detailed sleep tips.

Find Your Ideal Sleep & Wake Times

The Science of Sleep Cycles

One Sleep Cycle = 90 Minutes

A Full Night's Sleep (5-6 Cycles)

Light Sleep (N1 & N2)

Deep Sleep (N3)

REM Sleep

Why Waking Mid-Cycle Feels Terrible

Frequently Asked Questions

Learn to Sleep Better

How Sleep Cycles Work: A Complete Guide

Find Your Best Bedtime Based on Wake Time

How Much Sleep Do Adults Really Need?