What is it?
The Sleep Calculator suggests bedtimes or wake-up times that line up with your sleep cycles, so you’re more likely to wake up fresh.
Who is it for?
Students with early classes, shift workers, and anyone who wakes up groggy and wants better sleep timing.
How to use it
- Choose I want to Wake up at… and enter the Time to get bedtimes, or Go to bed now / at… to get wake-up times.
- Set the Minutes to fall asleep (about 15 for most people).
Why cycles matter
Sleep comes in cycles of about 90 minutes. Waking at the end of a cycle helps you feel fresh. Adults need 7–9 hours, which is 5 or 6 cycles. Waking in the middle of deep sleep is what makes you groggy.
Better sleep
- Keep the same wake-up time every day, including weekends.
- Avoid screens and bright light for 30–60 minutes before bed; keep the room dark and cool.
- No caffeine after the afternoon, and no heavy meals late at night.
- Teenagers need 8–10 hours, children more.
Cycle length varies from person to person (70–120 minutes). If you snore loudly, stop breathing in sleep, or are always tired, see a doctor.
Worked example
To wake at 6:30 am with 15 minutes to fall asleep, good bedtimes are 9:15 pm, 10:45 pm or 12:15 am (6, 5 or 4 cycles).
Errors and how to fix them
- No times shown: choose a time first.
Open the tool: Sleep Calculator
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.