Sleep calculator
Find out when to go to bed or get up. Free, no account needed, and worked out in your browser.
Your night
- Get into bed
- 10:45 PM
- Estimated time asleep
- 11:00 PM
- Wake up
- 7:00 AM next day
- Planned sleep
- 8 h
- Time in bed
- 8 h 15 min
An estimate to help plan your evening, not a measurement of your sleep.
How the calculation works
It's simple clock arithmetic. It starts from what you know, your wake-up time or your bedtime, and adds two settings: how much sleep you're aiming for and how long you take to fall asleep.
That's why the result shows two lengths of time. Time in bed starts when you lie down; planned sleep starts only once you've fallen asleep.
- Bedtime = wake-up time − sleep wanted − time to fall asleep
- Wake-up time = bedtime + time to fall asleep + sleep wanted
Example bedtimes
When to get into bed for each wake-up time and sleep target, allowing 15 minutes to fall asleep.
| Wake up | 7 h | 7 h 30 min | 8 h | 9 h |
|---|---|---|---|---|
| 6:00 AM | 10:45 PM | 10:15 PM | 9:45 PM | 8:45 PM |
| 6:30 AM | 11:15 PM | 10:45 PM | 10:15 PM | 9:15 PM |
| 7:00 AM | 11:45 PM | 11:15 PM | 10:45 PM | 9:45 PM |
| 7:30 AM | 12:15 AM | 11:45 PM | 11:15 PM | 10:15 PM |
| 8:00 AM | 12:45 AM | 12:15 AM | 11:45 PM | 10:45 PM |
Sleep duration and the limits of sleep cycles
The CDC recommends 7 hours or more for adults aged 18 to 60. France's Inserm also gives 7 hours a day as the usual recommended minimum, and France's national health insurance suggests planning for about 8 hours, more or less depending on your needs. Those needs vary a lot from one person to another.
Both the CDC and French health insurance advise keeping regular hours. So when you choose your settings, enough sleep and a steady routine come first.
According to Inserm, a night contains 3 to 6 cycles of 60 to 120 minutes. The often-quoted 90 minutes is an average, and this tool has no way of knowing how long your own cycles are. It therefore does not calculate sleep stages or try to wake you between cycles. Cutting a night short to "finish a cycle" makes no sense: getting enough sleep matters more.
Frequently asked questions
What time should I go to bed to wake up at 7 am?
For 8 hours of sleep and 15 minutes to fall asleep, get into bed at 10:45 pm. For 7 hours of sleep, at 11:45 pm.
How many hours of sleep do I need?
There's no single number for everyone. The CDC recommends 7 hours or more for adults aged 18 to 60, and individual needs vary widely.
Why 15 minutes to fall asleep by default?
It's a starting value chosen for this tool, not a standard: the sources cited here don't set a figure. Adjust it to your usual evenings, from 0 to 90 minutes.
Can this tool guarantee I wake up refreshed?
No. It organizes times; it doesn't measure your cycles or how well you sleep.
Who is this calculator for?
Adults. It isn't designed for babies, children or people who work nights.
When should I talk to a doctor?
If you've been sleeping badly for several weeks despite good habits, French health insurance advises talking to your doctor.
Are my times saved?
No. The calculation runs in your browser: your times are neither sent anywhere nor stored.
Sources
- Inserm, Sommeil ()
- Assurance Maladie (ameli.fr), Comment mieux dormir à l'âge adulte ? ()
- Assurance Maladie (ameli.fr), Insomnie de l'adulte : consultation et bilan médical ()
- CDC, About Sleep ()
Page reviewed on .
This tool offers planning guidance. It doesn't replace medical advice and doesn't diagnose anything.