Sleep Cycle Calculator

Find the best bedtime or wake-up time based on 90-minute sleep cycles so you wake up refreshed.

Fall asleep by
05:15
1 cycle · 1h 30m of sleep
Fall asleep by
03:45
2 cycles · 3h 00m of sleep
Fall asleep by
02:15
3 cycles · 4h 30m of sleep
recommended
Fall asleep by
00:45
4 cycles · 6h 00m of sleep
recommended
Fall asleep by
23:15
5 cycles · 7h 30m of sleep
(night before)
Fall asleep by
21:45
6 cycles · 9h 00m of sleep
(night before)

Sleep cycles average ~90 minutes (you go through lighter and deeper stages). This tool assumes you fall asleep in the 15-minute buffer. It's a planning aid — everybody differs; chronotype and sleep debt matter too.

About Sleep Cycle Calculator

Find the best bedtime or wake-up time based on 90-minute sleep cycles so you wake up refreshed.

Sleep Cycle Calculator does calendar-aware date and time math for you, handling leap years and variable month lengths so the numbers you get are correct.

How to Use Sleep Cycle Calculator

  1. Enter the date, time or duration values requested.
  2. Choose any options such as format or inclusive counting.
  3. The result appears instantly.
  4. Copy the output if you need to keep it.

Key Features

  • Calendar-accurate results, including leap years.
  • Instant answers with a clear, readable format.
  • No timezone setup required for everyday date math.

Frequently Asked Questions

Does Sleep Cycle Calculator account for leap years?

Yes. Date and time calculations account for leap years and the differing lengths of months, so durations and differences are accurate.

Is Sleep Cycle Calculator free to use?

Yes. Sleep Cycle Calculator is completely free with unlimited use — no account, download or payment required.

Is my data uploaded to a server?

No. Sleep Cycle Calculator runs entirely in your browser. Your inputs are never sent to our servers or stored anywhere.

Does Sleep Cycle Calculator work on mobile?

Yes. The interface is fully responsive and works in any modern browser on Android, iPhone, tablets and desktops.

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