Sleep Calculator

Find the best bedtimes for your wake-up time so you wake at the end of a 90-minute sleep cycle.

What is the Sleep Calculator?

Sleep runs in cycles of about 90 minutes. Waking in the middle of deep sleep leaves you groggy, while waking between cycles feels easier.

How does it work?

The calculator counts back 6, 5, 4 or 3 cycles plus the time you usually take to fall asleep.

Formula

Bedtime = Wake time − (cycles × 90 min) − time to fall asleep

Example

To wake at 6:30 AM, aim to sleep at 9:15 PM (6 cycles) or 10:45 PM (5 cycles).

Frequently asked questions

How much sleep do I need?

Most adults need 7–9 hours; teenagers 8–10. Individual needs vary.

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