Sleep Calculator
Find the best times to go to bed or wake up based on 90-minute sleep cycles.
Go to bed at one of these times for a natural, refreshed wake-up.
Sleep at
9:46 PM
6 cycles · 9 hours of sleep · recommended
- 5 cycles · 7.5 hours of sleep
- Sleep at 11:16 PM
- 4 cycles · 6 hours of sleep
- Sleep at 12:46 AM
- 3 cycles · 4.5 hours of sleep
- Sleep at 2:16 AM
Based on 90-minute sleep cycles and about 14 minutes to fall asleep. Waking at the end of a cycle helps you feel less groggy.
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How to use it
- 1
Choose a mode
Set a wake-up time, or start from going to sleep now.
- 2
Read the options
Each option is a whole number of 90-minute cycles.
- 3
Pick the best fit
The top option (recommended) gives a full night's rest.
Perfect for every need
Wake up refreshed
Time your sleep to end at the light phase of a cycle, not mid-cycle.
- Early meetings
- Flights
- Exams
Naps
Plan a short nap that ends at a natural point.
- Power naps
- Shift work
Kids' bedtimes
Work back from a wake time to a consistent bedtime.
- School mornings
- Routines
Frequently asked questions
How does the sleep calculator work?
Sleep happens in cycles of about 90 minutes. Waking at the end of a cycle feels easier than waking in the middle. The calculator counts whole 90-minute cycles (plus ~14 minutes to fall asleep) to suggest bedtimes or wake times.
How many cycles should I aim for?
Most adults do well with 5–6 cycles (about 7.5–9 hours). The top suggestion is 6 cycles; shorter options are there for nights when that isn't possible.
Is this medical advice?
No. It's a simple planning aid based on average sleep-cycle length. Individual needs vary.