Sleep calculator
Pick when you need to wake up to see good bedtimes — or go to bed now and see when to set the alarm — based on roughly 90-minute sleep cycles.
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How sleep cycles work
Sleep moves through light sleep, deep sleep and REM sleep in cycles of roughly 80–110 minutes, repeated four to six times a night. Waking at the end of a cycle, during lighter sleep, tends to feel easier than being woken from deep sleep. The 90-minute figure is an average — yours may differ, so adjust the cycle length if you consistently wake groggy.
How much sleep do you need?
| Teens (14–17) | 8–10 hours |
| Adults (18–64) | 7–9 hours |
| Older adults (65+) | 7–8 hours |
These are the ranges in Canada’s 24-Hour Movement Guidelines. A consistent wake-up time, even on weekends, does more for sleep quality than any single bedtime. If you snore loudly, stop breathing during sleep or are always tired, talk to a doctor.
Wind down with a timer: try the focus timer for the day and stop screens an hour before bed.
Frequently asked questions
What time should I go to bed to wake up at 7 am?
For five or six 90-minute cycles plus 15 minutes to fall asleep: 9:45 pm or 11:15 pm.
Is 6 hours of sleep enough?
For most adults, no. Health guidelines recommend at least 7 hours.
Why do I feel worse after a long nap?
Waking from deep sleep causes grogginess (sleep inertia). Keep naps to about 20 minutes, or a full 90-minute cycle.