Sleep Cycle Calculator
Work out the best times to go to bed or set your alarm, built from 90-minute sleep cycles so you wake between cycles feeling fresher. Runs in your browser.
Suggested times
How it works
Sleep runs in cycles of about 90 minutes. Waking at the end of a cycle, rather than in the middle of deep sleep, tends to feel more refreshing. The times below are built from whole cycles, plus about 15 minutes to fall asleep. Five or six cycles (7½–9 hours) suits most adults.
Cycle length is an average and varies from person to person and night to night, so treat these as a helpful guide, not a rule. Everything is computed in your browser.
What this does
A sleep cycle calculator works out the best times to go to bed or set your alarm, built from 90-minute sleep cycles so you wake between cycles feeling fresher.
How to use it
- Choose to set a bedtime or a wake-up time.
- Enter the time.
- Read the suggested times.
- Pick one of the recommended options.
How it works
Sleep runs in cycles of about 90 minutes. The times are built from whole cycles, plus about 15 minutes to fall asleep, so you wake between cycles rather than mid-cycle.
bedtime = wake time − (90 min × cycles) − 15 min
Understanding your result
The suggested times aim to wake you between 90-minute cycles rather than mid-cycle, which is why waking can feel easier even on slightly less sleep. Cycle length varies from person to person, so treat the times as a starting point and shift them 10 or 15 minutes if you still wake groggy, and do not use cycle timing as a reason to cut your total sleep short.
Example
To wake at 7:00, good bedtimes are about 21:45 or 23:15 (six or five cycles).
Sources & methodology
Last updated .
Frequently asked questions
How does it work?
Sleep runs in cycles of about 90 minutes. The times are built from whole cycles, plus about 15 minutes to fall asleep, so you wake between cycles rather than mid-cycle.
How many cycles should I aim for?
Five or six cycles (roughly 7½ to 9 hours) suits most adults. The recommended options are marked.
Is this medical advice?
No. Cycle length is an average and varies from person to person, so treat the times as a helpful guide. Everything is computed in your browser.
Related tools
Smoking Cost Calculator
See what a smoking habit costs per day, week, month, year and decade from your cigarettes per day and pack price. Calculated in your browser.
Love Compatibility Calculator
A just-for-fun compatibility percentage for two names, from a stable hash so the same pair always scores the same. Runs in your browser, nothing is stored.
Anniversary Calculator
Count how long you’ve been together in years, months and days, with a countdown to the next anniversary and totals in weeks and days. Calculates in your browser.
Age Difference Calculator
Find the age gap between two people from their birth dates, in years, months and days, plus totals in weeks and months, and who is older. Runs in your browser.