How does the sleep calculator work?
While you sleep, your brain moves through sleep cycles of about 90 minutes, alternating between light sleep, deep sleep and REM sleep. Waking up at the end of a cycle, when sleep is lighter, is usually much easier than waking up in the middle of deep sleep.
The calculator counts in 90-minute blocks from the time you choose and adds about 15 minutes, the average time it takes to fall asleep.
How many hours of sleep do I need?
Most adults are advised to get 7 to 9 hours a night; teenagers need 8 to 10. In cycles, that's 5 or 6 full cycles (7.5 or 9 hours), which is why the calculator marks them as recommended.
Why do I wake up tired even after 8 hours?
That groggy feeling when you wake up is called sleep inertia. It's stronger when your alarm goes off in the middle of a deep sleep cycle, even if you slept enough.
Hitting snooze doesn't help either: every "just 5 more minutes" starts light, fragmented sleep that isn't restful and leaves you even more tired.
How to wake up at the time you chose
Calculating the time is half the job. The other half is getting up when the alarm rings:
- Wake up at the same time every day, weekends included.
- Get natural light as soon as you're up.
- Avoid screens and caffeine in the hours before bed.
- Don't hit snooze.
- Move your body or wake up your brain in the first few minutes.
LevoUp combines the last two tips: the alarm won't turn off until you complete a mission, like solving a math problem or snapping the sky. So you're up on the first ring.
Frequently asked questions
What time should I go to bed to wake up at 6 AM?
For 5 cycles (7.5 hours), go to bed at 10:15 PM. For 6 cycles (9 hours), at 8:45 PM. Both times include 15 minutes to fall asleep.
What time should I go to bed to wake up at 7 AM?
Go to bed at 11:15 PM for 5 cycles (7.5 hours) or at 9:45 PM for 6 cycles (9 hours).
Is it better to sleep 6 hours or 7.5 hours?
7.5 hours. Waking up at the end of a cycle can make 6 hours feel better than an interrupted 7, but most adults need at least 7 hours to perform well.
Do sleep cycles always last 90 minutes?
No. They usually last between 80 and 120 minutes and change throughout the night. Use the calculator as a starting point and adjust by 15 minutes if you wake up groggy.
Does it work for naps?
Yes. A short nap of about 20 minutes avoids deep sleep; if you have more time, try to complete a full cycle of about 90 minutes.