Question 1

How does the sleep calculator work?

Accepted Answer

LunaSleep's sleep calculator uses the science of 90-minute sleep cycles. Each full cycle includes light sleep, deep sleep, and REM sleep. The calculator adds 14 minutes for average time to fall asleep, then calculates wake-up times (or bedtimes) that align with the end of a complete cycle — so you wake up between cycles rather than mid-cycle, reducing grogginess.

Question 2

How many hours of sleep should I get?

Accepted Answer

Most adults need 7–9 hours of sleep per night, which corresponds to 5–6 complete 90-minute sleep cycles. Teenagers need 8–10 hours (5–6 cycles), and younger children need more. Quality matters as much as quantity — waking at the end of a cycle makes even 6 hours feel more refreshing than 8 hours of interrupted sleep.

Question 3

What is the best time to wake up?

Accepted Answer

The best time to wake up is at the end of a complete 90-minute sleep cycle. If you fall asleep at 10:30 PM (accounting for ~14 minutes to fall asleep), ideal wake times would be around 5:14 AM (6 cycles), 6:44 AM (7 cycles), or 4:14 AM (5 cycles). Use LunaSleep's calculator to find your personalized optimal wake time.

Question 4

What are sleep cycles and why do they matter?

Accepted Answer

Sleep cycles are approximately 90-minute recurring patterns that include four stages: N1 (light sleep), N2 (light sleep), N3 (deep/slow-wave sleep), and REM (rapid eye movement). Waking up mid-cycle — especially during deep sleep — causes sleep inertia (that groggy feeling). Waking at the end of a cycle, typically during lighter REM or N1 sleep, allows you to feel alert and refreshed.

Question 5

Is LunaSleep free to use?

Accepted Answer

Yes, LunaSleep is completely free to use. All features including the sleep calculator, sleep tracker, ambient sounds library, sleep hygiene checklist, and dashboard insights are available at no cost. No subscription or credit card is required.

Question 6

Can I track my sleep history with LunaSleep?

Accepted Answer

Yes. LunaSleep includes a full sleep tracker where you can log your bedtime, wake time, sleep quality, mood, and environmental factors each night. The dashboard shows trends, sleep score, quality distribution, and smart personalized insights based on your last 30 nights of data.

Question 7

Does the sleep calculator work on mobile?

Accepted Answer

Yes, LunaSleep is fully responsive and works on all devices including iPhone, Android phones, tablets, and desktop browsers. The app supports mobile-optimized navigation, pull-to-refresh, and ambient sound playback on all platforms.

Tips | LunaSleep - Sleep Cycle Calculator

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