Question 1

What time should I go to sleep?

Accepted Answer

Use the Wake Up mode in the Sleep Calculator: enter the time you need to wake up and the calculator will show you the best bedtimes based on 90-minute sleep cycles. For 7.5 hours (5 cycles), go to bed 8 hours before your alarm (including ~15 min to fall asleep).

Question 2

How long is a sleep cycle?

Accepted Answer

One complete sleep cycle lasts approximately 90 minutes and includes light sleep, deep (slow-wave) sleep, and REM sleep. Most adults need 4–6 complete cycles per night (6–9 hours). Waking up at the end of a cycle — rather than in the middle — is what makes you feel refreshed instead of groggy.

Question 3

Is a 20-minute nap better than a 30-minute nap?

Accepted Answer

Yes. A 20-minute (power) nap keeps you in light sleep stages and lets you wake up alert. A 30-minute nap risks entering deep sleep, causing sleep inertia — the groggy, disoriented feeling that can last 30+ minutes. Either nap for 10–20 minutes (power nap) or a full 90 minutes (complete cycle). Avoid the 30–60 minute grogginess zone.

Question 4

What is a chronotype?

Accepted Answer

A chronotype is your body's natural preference for sleep and wake times, largely determined by genetics. Morning larks feel alert early and tire early; night owls peak in the evening and struggle with early mornings. About 30% of people are larks, 30% owls, and 40% intermediate. Knowing your chronotype lets you schedule sleep and work for peak performance.

Question 5

What is the best time to take a power nap?

Accepted Answer

The ideal power nap window is 7–8 hours after you wake up — for most people, that's between 1 PM and 3 PM. Napping later risks interfering with nighttime sleep. Keep it to 10–20 minutes. The "caffeine nap" technique — drinking coffee right before a 20-minute nap — lets you wake up as the caffeine kicks in for a double energy boost.

Question 6

How many hours of sleep do I need?

Accepted Answer

Most adults need 7–9 hours (4–6 complete 90-minute sleep cycles). 5 cycles (7.5 hours) is the scientific sweet spot for most people. Consistently getting fewer than 4 cycles (6 hours) accumulates sleep debt that impairs memory, focus, and immune function. Use the Sleep Calculator to find your personal optimal based on your wake time and chronotype.