Most adults feel best after 5 or 6 full cycles (7.5-9 hours). The calculator marks the recommended wake time in green and the others as options. Use it before bed to time the alarm, or in the morning to plan when to head to bed tonight.
Calculator
Formula used
Cycle end = bedtime + latency + N × 90 min · N = 1 to 6 cycles
How to use the Sleep Cycle Calculator
- Pick whether you start from a bedtime or a desired wake time.
- Type the time in 24-hour format (HH:MM).
- Adjust the sleep latency if you tend to fall asleep quickly or slowly.
- Read the recommended wake time and the alternative cycle ends.
About this tool
The Sleep Cycle Calculator is built for speed and accuracy: every calculation runs in your browser, so your data never leaves your device and the result updates as you type. It works equally well on a phone, a tablet or a desktop, and it is free to use as many times as you like.
Common use cases
- Setting a smart alarm before bed.
- Planning a power nap (1 cycle = 90 minutes).
- Working backwards from an early meeting.
- Catching up after a poor night of sleep.
Tips for the best result
- Use the latest figures you have - even a small change in rate or term can shift the outcome by hundreds.
- For annual figures, divide by 12 to get a monthly number you can compare with the result.
- Bookmark this page and revisit the calculation as the inputs change.
Frequently asked questions
How long is a sleep cycle?
About 90 minutes on average, varying from 70 to 110. The calculator uses 90 as a standard.
What if I wake in the middle of a cycle?
That is normal; you will feel groggy for 15-30 minutes. Get up, get some light and the effect fades. Use the calculator to plan the alarm so you are near the end of a cycle.
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