Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
100% private — everything runs in your browser
How to Use
- 1
Choose whether you know your bedtime or your wake-up time.
- 2
Set the time and how long you usually take to fall asleep.
- 3
Pick a suggested slot — each one lands at the end of a full cycle.
Examples
Wake at 07:00
Input
Wake-up: 07:00 · 15 min to fall asleepOutput
Bedtimes around 21:45, 23:15 or 00:45 give 6, 5 or 4 full cycles.Bed at 23:00
Input
Bedtime: 23:00 · 15 min latencyOutput
Wake-up options around 05:45, 07:15 or 08:45.FAQ
How accurate is this?
It is a planning aid based on average 90-minute cycles. Real cycles vary by person and by night.
Why add time to fall asleep?
Cycles start after you fall asleep, not when you lie down, so the latency shifts every suggestion.
Is 6 cycles always best?
No. Many people feel better after 5 cycles than after a forced 6. Pick the slot that fits your schedule.
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