Bedtime · Wake time · Nap calculator
Sleep calculator
Estimate bedtime and wake-time ranges from sleep cycles. Cycles vary between people and across the night. Adjust the assumptions to see how the times change.
Default: 90 · Allowed: 60–150
Default: 15 · Allowed: 0–60
Bedtime estimates
Latest first. Day labels are relative to your wake-time day.
Times use your local clock. Calculations run in your browser. Your inputs are not sent to a server or saved.
What this does not tell you
This calculator cannot identify your sleep stages, tell you how much sleep you need or predict how you will feel when you wake. The options are calculations, not recommended sleep durations. No source below tests a benefit from waking at a chosen cycle boundary.
Set a sleep timer for the sound you fall asleep to: Brown noise or Rain.
How this is calculated
Bedtime = wake time − (cycles × cycle length) − time to fall asleep. Wake time = bedtime + time to fall asleep + (cycles × cycle length).
Each option shows the time at your chosen cycle length and a separate comparison range using 80- and 110-minute cycles, with your chosen latency in both. This range illustrates how the assumption changes the result. It is not a confidence interval or the full observed spread. A cycle length outside 80–110 minutes can put your chosen time outside the comparison range.
For naps, wake time = start time + time to fall asleep + 20 or 90 minutes. The nap range keeps that duration fixed and uses 0–60 minutes to fall asleep. It is an input comparison, not a prediction.
Cycles vary between people and across the night. Neither range accounts for time awake during sleep. Day labels track midnight crossings relative to the entered time. These clock estimates use no date and do not adjust for daylight-saving clock changes.
What this is based on
Carskadon & Dement, Normal Human Sleep: An Overview describes first cycles averaging 70–100 minutes and later cycles around 90–120 minutes.
Cajochen et al., 2024, Sleep Health reports a median cycle duration of 96 minutes and a 95% interval of 60–150 minutes across 6,064 recorded cycles in 369 healthy laboratory participants. That spread does not define a personal schedule.
Ohayon et al., 2017, Sleep Health reports an expert panel rating a latency of 15 minutes or less as indicating good sleep quality. The panel also rated 16–30 minutes as good. This was a consensus rating, not a measurement of how long you will take to fall asleep. Our 15-minute default is editable.
Frequently asked questions
What time should I go to bed if I wake at 7 am?
With 90-minute cycles and 15 minutes to fall asleep, the six-cycle calculation is 9:45 pm the previous day. The comparison using 80–110-minute cycles spans 7:45–10:45 pm. These are rough estimates, not a prescribed bedtime.
Is a sleep cycle always 90 minutes?
No. Cycles vary between people and across the night. Ninety minutes is a starting assumption. Changing that input shows how much the calculated times depend on it.
Does the nap calculator include time to fall asleep?
Yes. It adds your chosen latency to a fixed 20- or 90-minute nap. The comparison range uses 0–60 minutes to fall asleep. A 90-minute nap does not necessarily equal one sleep cycle. This page does not set an alarm.
Are three cycles enough sleep for me?
This calculator cannot tell you how much sleep you need. The three-to-six-cycle options show arithmetic, not recommended sleep durations. It does not measure your sleep or predict how you will feel.