# Sleep calculator: when to sleep and wake

> A wake-up time or a bedtime, and the sleep cycles between them, give the times for a good night.

Pick a wake-up time or a bedtime to see the times that fit 3 to 6 sleep cycles, with time to fall asleep included. Adults need 7 or more hours.

- Tool: [Sleep calculator](https://fixmint.cc/sleep-calculator)
- Category: [Numbers & dates](https://fixmint.cc/numbers)
- Fixes: When should I go to bed?
- Runs in the browser: files and text stay on the device, no sign-up, free.

## How to choose a bedtime or wake-up time

1. Choose "I wake up at" or "I go to bed at", and enter that time.
2. Set how many minutes you usually take to fall asleep.
3. Pick a card to see the night as a bar: falling asleep, then each sleep cycle.

## Questions

### How long is a sleep cycle?

The Cleveland Clinic says an average sleep cycle lasts about 90 minutes. Real cycles vary from person to person and from night to night, so the times here are a guide, not a promise.

### How much sleep do adults need?

The CDC says adults aged 18 to 60 should get 7 or more hours of sleep a night, in line with the 2015 consensus of the American Academy of Sleep Medicine and the Sleep Research Society. For adults 61 to 64 the CDC lists 7 to 9 hours, and for 65 and older 7 to 8 hours.

### Why do the times count whole cycles?

The tool adds whole cycles of about 90 minutes, plus the time to fall asleep, so each wake-up time lands at the end of a cycle. It cannot see your sleep stages, so treat the times as a plan, not a measurement.

### When should I talk to a doctor about sleep?

If you regularly have trouble falling or staying asleep, or feel very sleepy during the day, talk to a doctor. This tool does not diagnose sleep problems.

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